Filed Pursuant to Rule 424(b)(3)
Registration No. 333-294882

 

MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

To the Shareholders of Stellar Bancorp, Inc.

On behalf of the board of directors of Stellar Bancorp, Inc. (“Stellar”), we are pleased to enclose the accompanying proxy statement/prospectus relating to the proposed merger of Stellar with and into Prosperity Bancshares, Inc. (“Prosperity”). We are requesting that you take certain actions as a holder of shares of common stock of Stellar, par value $0.01 per share (“Stellar common stock”).

The boards of directors of Stellar and Prosperity (the “Stellar Board” and “Prosperity Board,” respectively) have each unanimously approved the Agreement and Plan of Merger, dated January 27, 2026, by and between Stellar and Prosperity (as amended from time to time, the “merger agreement”), pursuant to which Stellar will merge with and into Prosperity (the “merger”), with Prosperity as the surviving corporation. Immediately following the merger, Stellar Bank, a wholly owned subsidiary of Stellar, will merge with and into Prosperity Bank, a wholly owned subsidiary of Prosperity, with Prosperity Bank as the surviving bank.

In the merger, each holder of shares of Stellar common stock (a “Stellar shareholder”) will receive (i) $11.36 in cash (the “per share cash consideration”) and (ii) 0.3803 shares (the “exchange ratio”) of Prosperity common stock, par value $1.00 per share (“Prosperity common stock”) for each share of Stellar common stock they own as of the effective time of the merger (the consideration described in clauses (i) and (ii) together, the “per share merger consideration” and the aggregate of such consideration, the “merger consideration”). Stellar shareholders will receive cash in lieu of fractional shares of Prosperity common stock issuable as a result of the merger. Holders of Prosperity common stock will continue to own their existing shares of Prosperity common stock. Based on the closing price of Prosperity common stock on the New York Stock Exchange (the “NYSE”) on January 27, 2026, the last trading day before public announcement of the merger, of $72.90, the per share merger consideration represented approximately $39.08 in value for each share of Stellar common stock, which represented merger consideration of approximately $2.0 billion on an aggregate basis. Based on the closing price of Prosperity common stock on the NYSE on April 15, 2026, the last practicable trading day before the date of this proxy statement/prospectus, of $69.12, the per share merger consideration represented approximately $37.65 in value for each share of Stellar common stock. The price of Prosperity common stock at the time of completion of the merger could be greater than, less than or the same as the price of Prosperity common stock on the date of this proxy statement/prospectus, which could affect the value of the per share merger consideration. We urge you to obtain current market quotations of Prosperity common stock (trading symbol “PB”) and Stellar common stock (trading symbol “STEL”).

Based on the number of shares of Stellar common stock outstanding as of April 15, 2026, Prosperity expects to issue approximately 19,361,338 shares of Prosperity common stock to holders of Stellar common stock (in the aggregate) and to pay approximately $578,345,529 in cash in the merger. Based on the number of shares of Stellar common stock and Prosperity common stock outstanding as of April 15, 2026, we estimate that, following the completion of the merger, former holders of Stellar common stock will own approximately 16.1% of the combined company and existing Prosperity holders will own approximately 83.9% of the combined company.

The special meeting of Stellar shareholders (the “special meeting”) will be held at our corporate headquarters, which is located at 9 Greenway Plaza, Eighth Floor – Galveston Conference Room, Houston, Texas 77046, on May 27, 2026, at 10:00, a.m., Central Time. At the special meeting, Stellar will ask Stellar shareholders to approve the merger agreement, approve certain merger-related compensation, and approve an adjournment of the meeting (if necessary). Information about the special meeting and the merger is contained in the accompanying proxy statement/prospectus. In particular, see the section entitled “Risk Factors” beginning on page 20. We urge you to read this document carefully and in its entirety. You can also obtain

information about Stellar and Prosperity from documents that have been filed with the U.S. Securities and Exchange Commission (the “SEC”) that are incorporated into the accompanying proxy statement/prospectus by reference.

Whether or not you plan to attend the special meeting, please vote as soon as possible to make sure that your shares are represented at the special meeting. If you do not vote, it will have the same effect as voting “AGAINST” the merger.

The Stellar board of directors unanimously recommends that holders of Stellar common stock vote “FOR” each of the proposals to be considered at the special meeting.

 

Sincerely,

Steven F. Retzloff Chairman of the Board Stellar Bancorp, Inc.

Neither the SEC nor any state securities regulator has approved or disapproved of the securities to be issued in connection with the merger or passed upon the adequacy of the accompanying proxy statement/prospectus. Any representation to the contrary is a criminal offense.

The shares of Prosperity common stock to be issued in the merger are not savings accounts, deposits or other obligations of any bank or savings association and are not insured by the Federal Deposit Insurance Corporation (the “FDIC”) or by any other U.S. federal or state governmental agency.

The accompanying proxy statement/prospectus is dated April 21, 2026, and is first being mailed to Stellar shareholders on or about April 23, 2026.

Stellar Bancorp, Inc.

9 Greenway Plaza, Suite 110

Houston, Texas 77046

(713) 210-7600

 

 

NOTICE OF SPECIAL MEETING OF SHAREHOLDERS

 

 

To the Shareholders of Stellar Bancorp, Inc.:

The special meeting of shareholders (the “special meeting”) of Stellar Bancorp, Inc. (“Stellar”) will be held at our corporate headquarters, which is located at 9 Greenway Plaza, Eighth Floor – Galveston Conference Room, Houston, Texas 77046, on May 27, 2026, at 10:00 a.m., Central Time.

At the special meeting, you will be asked to consider and vote on the following:

 

•

a proposal to approve the Agreement and Plan of Merger, dated January 27, 2026 (as amended from time to time, the “merger agreement”), a copy of which is attached as Annex A to the accompanying proxy statement/prospectus of which this notice is a part, by and between Stellar and Prosperity Bancshares, Inc. (“Prosperity”), and the transactions contemplated thereby, including the merger of Stellar with and into Prosperity (the “merger”) (the “merger proposal”);

 

•

a proposal to approve, on a non-binding, advisory basis, the compensation that may be paid or become payable to Stellar’s named executive officers that is based on or otherwise relates to the merger (the “merger compensation proposal”); and

 

•

a proposal to adjourn or postpone the special meeting, if necessary or appropriate, to solicit additional proxies if, immediately prior to such adjournment or postponement, there are not sufficient votes to approve the merger proposal or to ensure that any supplement or amendment to the accompanying proxy statement/prospectus is timely provided to holders of Stellar common stock (the “adjournment proposal”).

The proposals are described in the accompanying proxy statement/prospectus. The Board of Directors of Stellar (the “Stellar Board”) has fixed the close of business on April 10, 2026 as the record date for the special meeting. Only holders of record of Stellar common stock as of the close of business on the record date for the special meeting are entitled to notice of, attend and to vote at, the special meeting or any adjournment or postponement thereof. Stellar will transact no other business at the special meeting, except for business properly brought before the special meeting or any adjournment or postponement thereof.

The Stellar Board has unanimously approved the merger agreement and the transactions contemplated by the merger agreement, including the merger, and unanimously recommends that Stellar shareholders vote “FOR” the merger proposal, “FOR” the merger compensation proposal and “FOR” the adjournment proposal.

Your vote is important, regardless of the number of shares you own. We cannot complete the transactions contemplated by the merger agreement, including the merger, unless the holders of Stellar common stock approve the merger proposal. The affirmative vote of the holders of at least two-thirds of the outstanding shares of Stellar common stock entitled to vote thereon at the special meeting is required to approve the merger proposal.

Assuming a quorum is present, approval of the merger compensation proposal and adjournment proposal each require the affirmative vote of a majority of the votes cast by holders of Stellar common stock entitled to vote at the special meeting.

Stellar shareholders have the right to dissent from the merger and obtain payment in cash of the appraised fair value of their shares of Stellar common stock under applicable provisions of the Texas Business Organizations Code (the “TBOC”). In order for such Stellar shareholder to perfect his, her or its right to dissent, the shareholder must file a written objection to the merger with Stellar prior to the special meeting, vote against the merger agreement, file a written demand with Prosperity within twenty (20) days after the date Prosperity sends the shareholder notice of the completion of the merger for payment of the fair value of the shareholder’s shares of Stellar common stock, and comply with all other applicable requirements of Texas law. A copy of the applicable statutory provisions of the TBOC is included as Annex E to the accompanying proxy statement/prospectus and a summary of these provisions can be found under the caption “The Merger—Appraisal or Dissenters’ Rights in the Merger” beginning on page 89.

Each copy of the proxy statement/prospectus mailed to Stellar shareholders is accompanied by a form of proxy card with instructions for voting. Whether or not you plan to attend the special meeting, we urge you to please promptly complete, sign, date and return the accompanying proxy card in the enclosed postage-paid envelope or authorize the individuals named on the accompanying proxy card to vote your shares by calling the toll-free telephone number or by using the Internet as described in the instructions included with the accompanying proxy card. If your shares are held in the name of a bank, broker, trustee or other nominee, please follow the instructions on the voting instruction card furnished by such bank, broker, trustee or other nominee.

The proxy statement/prospectus of which this notice is a part provides a detailed description of the merger agreement, the transactions contemplated thereby, including the merger, and the other matters to be considered at the special meeting. A summary of the merger agreement is included in the proxy statement/prospectus in the sections entitled “The Merger” and “The Merger Agreement,” and a copy of the merger agreement is attached as Annex A to the proxy statement/prospectus, each of which are incorporated by reference into this notice to the same extent as if fully set forth herein. We encourage you to carefully read this proxy statement/prospectus (including the annexes thereto) and any other documents incorporated by reference herein in their entirety.

If you have any questions regarding the accompanying proxy statement/prospectus or need assistance with voting, you may contact Georgeson LLC, Stellar’s proxy solicitor, by calling toll-free at (877) 811-4522, or non-toll free at (267) 281-9853.

 

		By Order of the Stellar Board of Directors,
		Steven F. Retzloff Chairman of the Board Stellar Bancorp, Inc.
April 21, 2026

ADDITIONAL INFORMATION

This proxy statement/prospectus incorporates important business and financial information about Prosperity and Stellar from other documents filed with the SEC that have not been included in or delivered with this proxy statement/prospectus. This information is described on page 137 under the section entitled “Where You Can Find More Information.” You can obtain free copies of this information through the SEC website at http://www.sec.gov or by requesting it in writing or by telephone at the appropriate address below:

if you are a Prosperity shareholder:

Prosperity Bancshares, Inc.

Attention: Investor Relations

Prosperity Bank Plaza

4295 San Felipe

Houston, Texas 77027

(281) 269-7199

if you are a Stellar shareholder:

Stellar Bancorp, Inc.

Attention: Investor Relations

9 Greenway Plaza, Suite 110

Houston, Texas 77046

(713) 210-7600

You will not be charged for any of these documents that you request. To obtain timely delivery of these documents, you must request them by May 19, 2026 in order to receive them before the special meeting.

You should rely only on the information contained or incorporated by reference in this proxy statement/prospectus. No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this proxy statement/prospectus. This proxy statement/prospectus is dated April 21, 2026, and you should assume that the information in this document is accurate only as of such date. You should assume that the information incorporated by reference into this proxy statement/prospectus is accurate as of the date of such incorporated document. Neither the mailing of this proxy statement/prospectus to holders of Stellar common stock nor the issuance by Prosperity of shares of Prosperity common stock in connection with the merger will create any implication to the contrary.

This proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy, in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Except where the context otherwise indicates, information contained in, or incorporated by reference into, this proxy statement/prospectus regarding Stellar has been provided by Stellar and information contained in, or incorporated by reference into, this proxy statement/prospectus regarding Prosperity has been provided by Prosperity.

In addition, if you are a Stellar shareholder and have questions about the merger or this proxy statement/prospectus, would like additional copies of this proxy statement/prospectus or need to obtain proxy cards or other information related to the proxy solicitation, contact Georgeson LLC, the Stellar proxy solicitor, by calling toll-free at (877) 811-4522, or non-toll free at (267) 281-9853. You will not be charged for any of these documents that you request.

See the section entitled “Where You Can Find More Information” beginning on page 137 of this proxy statement/prospectus for further information.

TABLE OF CONTENTS

 

QUESTIONS AND ANSWERS			1
SUMMARY			11
The Parties to the Merger			11
The Merger and the Merger Agreement			12
Merger Consideration			12
Treatment of Stellar Equity Awards			13
Material U.S. Federal Income Tax Consequences of the Merger			14
Stellar’s Reasons for the Merger; Recommendation of the Stellar Board of Directors			14
Opinion of Stellar’s Financial Advisor			14
Appraisal or Dissenters’ Rights in the Merger			15
Interests of Stellar’s Directors and Executive Officers in the Merger			15
Expected Timing of the Merger			16
Conditions to Completion of the Merger			16
Termination of the Merger Agreement			17
Termination Fee			18
Accounting Treatment			18
The Rights of Holders of Stellar Common Stock Will Change as a Result of the Merger			18
Listing of Prosperity Common Stock; Delisting and Deregistration of Stellar Common Stock			18
The Special Meeting			18
Risk Factors			19
RISK FACTORS			20
UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION			29
CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS			39
THE SPECIAL MEETING			43
STELLAR PROPOSALS			49
INFORMATION ABOUT PROSPERITY			52
INFORMATION ABOUT STELLAR			53
THE MERGER			54
Terms of the Merger			54
Background of the Merger			54
Stellar’s Reasons for the Merger; Recommendation of the Stellar Board of Directors			61
Opinion of Stellar’s Financial Advisor			64
Certain Unaudited Prospective Financial Information			76
Interests of Stellar’s Directors and Executive Officers in the Merger			80
Governance of Prosperity After the Merger			86
Accounting Treatment			86
Regulatory Approvals			87
Stock Exchange Listings			89
Appraisal or Dissenters’ Rights in the Merger			89
THE MERGER AGREEMENT			92
Explanatory Note Regarding the Merger Agreement			92
Structure of the Merger			92
Merger Consideration			93
Fractional Shares			93
Governing Documents			93
Treatment of Stellar Equity Awards			93
Closing and Effective Time of the Merger			94
Conversion of Shares; Exchange of Stellar Common Stock Certificates			94
Representations and Warranties			95

 

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Covenants and Agreements			97
Special Meeting and Recommendation of the Stellar Board of Directors			105
Agreement Not to Solicit Other Offers			106
Conditions to Completion of the Merger			107
Termination of the Merger Agreement			108
Effect of Termination			109
Termination Fee			109
Fees and Expenses			110
Amendment, Waiver and Extension of the Merger Agreement			110
Voting Agreements			110
Director Support Agreements			111
Governing Law			111
Specific Performance			111
MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES OF THE MERGER			112
U.S. Federal Income Tax Consequences of the Merger Generally			114
Information Reporting and Backup Withholding			115
DESCRIPTION OF PROSPERITY CAPITAL STOCK			117
COMPARISON OF SHAREHOLDERS’ RIGHTS			120
TEXAS ANTI-TAKEOVER STATUTES			132
LEGAL MATTERS			134
EXPERTS			134
HOUSEHOLDING OF PROXY MATERIALS			135
SUBMISSION OF SHAREHOLDER PROPOSALS FOR STELLAR 2026 ANNUAL MEETING			136
WHERE YOU CAN FIND MORE INFORMATION			137
Annex A – Agreement and Plan of Merger			A-1
Annex B – Form of Voting Agreement			B-1
Annex C – Form of Director Support Agreement			C-1
Annex D – Opinion of Keefe, Bruyette & Woods, Inc.			D-1
Annex E – Provisions of the Texas Business Organizations Code Relating to Dissenters’ Rights			E-1

 

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QUESTIONS AND ANSWERS

The following are some questions that you may have about the merger and the special meeting, and brief answers to those questions. We urge you to read carefully the remainder of this proxy statement/prospectus because the information in this section does not provide all of the information that might be important to you with respect to the merger and the special meeting. Additional important information is also contained in the documents incorporated by reference into this proxy statement/prospectus. See the section entitled “Where You Can Find More Information” beginning on page 137.

In this proxy statement/prospectus, unless the context otherwise requires:

 

•

“Stellar” refers to Stellar Bancorp, Inc.;

 

•

“Stellar common stock” refers to the common stock, par value $0.01 per share, of Stellar;

 

•

“Prosperity” refers to Prosperity Bancshares, Inc.; and

 

•

“Prosperity common stock” refers to the common stock, par value $1.00 per share, of Prosperity.

 

Q:	Why am I receiving this proxy statement/prospectus?

 

A:

Stellar is holding a special meeting of shareholders (the “special meeting”) to (i) approve the Agreement and Plan of Merger, dated January 27, 2026 (as amended from time to time, the “merger agreement”), a copy of which is attached as Annex A to this proxy statement/prospectus, by and between Stellar and Prosperity, and the transactions contemplated thereby, including the merger (the “merger proposal”), (ii) approve, on a non-binding, advisory basis, the compensation that may be paid or become payable to Stellar’s named executive officers that is based on or otherwise relates to the merger (the “merger compensation proposal”), and (iii) obtain approval to adjourn or postpone the special meeting, if necessary or appropriate to solicit additional proxies if, immediately prior to such adjournment or postponement, there are not sufficient votes at the time of the special meeting to approve the merger proposal or to ensure that any supplement or amendment to this proxy statement/prospectus is timely provided to the holders of Stellar common stock (the “adjournment proposal”).

To complete the merger, among other things, holders of at least two-thirds of the outstanding Stellar common stock entitled to vote thereon at the special meeting must approve the merger proposal.

This document is also a prospectus that is being delivered to holders of Stellar common stock because, in connection with the merger, Prosperity is offering shares of Prosperity common stock to holders of Stellar common stock.

This proxy statement/prospectus contains important information about the merger agreement, the merger and the proposals being voted on at the special meeting. You should read it carefully and in its entirety. The enclosed materials allow you to have your shares of common stock voted by proxy without attending the special meeting. Your vote is important and we encourage you to submit your proxy as soon as possible.

 

Q:	What will happen in the merger?

 

A:

In the merger, Stellar will merge with and into Prosperity, with Prosperity continuing as the surviving corporation. After completion of the merger, Stellar will cease to exist and Prosperity will remain a publicly traded company. In addition, immediately following the completion of the merger, Stellar Bank, a Texas banking association and a wholly owned subsidiary of Stellar, will merge (the “bank merger”) with and into Prosperity Bank, a Texas banking association and a wholly owned subsidiary of Prosperity, with Prosperity Bank as the surviving bank (the “surviving bank”). See the information provided in the section entitled “The Merger Agreement—Structure of the Merger” beginning on page 92 and the merger agreement for more information about the merger.

 

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Q:	When and where will the special meeting take place?

 

A:

The special meeting is scheduled to take place at our corporate headquarters, which is located at 9 Greenway Plaza, Eighth Floor – Galveston Conference Room, Houston, Texas 77046, on Wednesday, May 27, 2026, at 10:00 a.m., Central Time. Even if you plan to attend the special meeting, Stellar recommends that you vote your shares in advance so that your vote will be counted if you later decide not to or become unable to attend the special meeting.

 

Q:	What matters will be considered at the special meeting?

 

A:	At the special meeting, holders of Stellar common stock will be asked to consider and vote on the following proposals:

 

•

Stellar Proposal 1: The merger proposal. Approval of the merger agreement and the transactions contemplated thereby, including the merger;

 

•

Stellar Proposal 2: The merger compensation proposal. Approval of, on a non-binding, advisory basis, the compensation that may be paid or become payable to Stellar’s named executive officers that is based on or otherwise relates to the merger; and

 

•

Stellar Proposal 3: The adjournment proposal. Approval of the adjournment or postponement of the special meeting, if necessary or appropriate, to solicit additional proxies if, immediately prior to such adjournment or postponement, there are not sufficient votes to approve the Stellar merger proposal or to ensure that any supplement or amendment to the accompanying proxy statement/prospectus is timely provided to holders of Stellar common stock.

In order to complete the merger, among other things, holders of at least two-thirds of the outstanding Stellar common stock entitled to vote thereon at the special meeting must approve the merger proposal. The approval of neither the merger compensation proposal nor the adjournment proposal is a condition to the obligations of Stellar or Prosperity to complete the merger.

 

Q:	What will holders of Stellar common stock receive in the merger?

 

A:

Under the terms and subject to the conditions set forth in the merger agreement, holders of Stellar common stock will receive (i) $11.36 in cash (the “per share cash consideration”) and (ii) 0.3803 shares (the “exchange ratio”) of Prosperity common stock (the consideration described in clauses (i) and (ii), the “per share merger consideration” and the aggregate of such consideration, the “merger consideration”) for each share of Stellar common stock issued and outstanding immediately prior to the effective time of the merger (excluding dissenting shares, treasury shares and shares held by Stellar or Prosperity (other than treasury shares and shares held by Stellar or Prosperity (a) held in any Stellar benefit plans or related trust accounts, managed accounts, mutual funds and the like, or otherwise held in a fiduciary or agency capacity and (b) held, directly or indirectly, in respect of debts previously contracted)). No fractional shares of Prosperity common stock will be issued in the merger, and holders of Stellar common stock who would otherwise be entitled to receive a fractional share will instead receive an amount in cash (rounded to the nearest cent) equal to such fraction multiplied by the average of the closing sale prices of Prosperity common stock on the NYSE for the ten (10) consecutive full trading days ending on and including the fifth (5th) trading day immediately preceding the closing date.

If the aggregate number of shares of Prosperity common stock to be issued in connection with the merger agreement (the “aggregate stock consideration”) would exceed nineteen and nine-tenths of a percent (19.9%) of the issued and outstanding shares of Prosperity common stock immediately prior to the effective time of the merger (the “Prosperity stock consideration cap”), (i) the exchange ratio will be reduced to the minimum extent necessary (rounded down to the nearest ten-thousandth when expressed in decimal form) such that the aggregate stock consideration does not exceed the Prosperity stock consideration cap and (ii) the per share cash consideration will be increased (for the avoidance of doubt, on a per share basis) by an

 

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amount in cash equal to the average of the closing sale prices of Prosperity common stock on the NYSE as reported by the Wall Street Journal for the ten (10) consecutive full trading days ending on and including the fifth (5th) trading day immediately preceding closing date (the “Prosperity share closing price”), multiplied by the difference between the initial exchange ratio and the exchange ratio as reduced (rounded down to the nearest whole cent).

 

Q:	What will holders of Prosperity common stock receive in the merger?

 

A:

In the merger, Prosperity shareholders will not receive any consideration, and their shares of Prosperity common stock will remain outstanding and will constitute shares of the surviving corporation. Following the merger, shares of Prosperity common stock will continue to be traded on the NYSE under the trading symbol “PB.”

 

Q:	Will the value of the merger consideration change between the date of this proxy statement/prospectus and the time the merger is completed?

 

A:

Yes. Although the per share cash consideration and the exchange ratio are fixed, the value of the merger consideration will fluctuate between the date of this proxy statement/prospectus and the completion of the merger based upon the market value of Prosperity common stock. Any change in the market price of Prosperity common stock prior to the completion of the merger will affect the value of the merger consideration that holders of Stellar common stock will receive upon completion of the merger. Neither Prosperity nor Stellar is permitted to terminate the merger agreement as a result, in and of itself, of any increase or decrease in the market price of Prosperity common stock.

 

Q:	How will the merger affect Stellar equity awards?

 

A:

At the effective time, (i) each Stellar stock option that has a per share exercise price that is less than the sum of (a) the per share cash consideration plus (b) the product of the exchange ratio multiplied by the Prosperity share closing price (the “per share merger consideration value”) (each, an “In-the-Money Option”) will be canceled and each holder thereof will have the right to receive (without interest) a cash payment equal to the product of (1) the per share merger consideration value minus the exercise price per share of Stellar common stock subject to such Stellar stock option as of immediately prior to the effective time multiplied by (2) the number of shares of Stellar common stock subject to such Stellar stock option as of immediately prior to the effective time, and (ii) each Stellar stock option that is not an In-the-Money Option and is outstanding and unexercised as of immediately prior to the effective time will be canceled for no consideration.

At the effective time, each Stellar restricted stock award will fully vest and be canceled and converted into the right to receive (without interest) the per share merger consideration in respect of each share of Stellar common stock subject to such Stellar restricted stock award immediately prior to the effective time plus any accrued but unpaid dividends, which will be delivered as soon as reasonably practicable following the closing date and in no event later than ten (10) business days following the closing date.

At the effective time, each Stellar performance unit award will be canceled and converted into the right to receive (without interest) a cash payment equal to the product of (i) the per share merger consideration value multiplied by (ii) the number of earned shares of Stellar common stock subject to such Stellar performance unit award as of immediately prior to the effective time (with achievement of applicable performance metrics determined to be equal to 100% of the target level (or, in the case of the performance units granted in 2024, 200% of the target level)) plus any accrued but unpaid dividend equivalents, which will be delivered as soon as reasonably practicable following the closing date and in no event later than ten (10) business days following the closing date (or any later date required by Section 409A of the Internal Revenue Code of 1986, as amended (the “Code”)).

 

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Each holder of a Stellar restricted stock award converted into the right to receive the per share merger consideration that would have otherwise been entitled to receive a fraction of a share of Prosperity common stock (after aggregating all shares to be delivered in respect of all Stellar restricted stock awards held by such holder) will instead receive a cash payment (rounded to the nearest cent) (without interest) in an amount equal to such fractional share of Prosperity common stock (rounded to the nearest thousandth when expressed in decimal form) multiplied by the Prosperity share closing price.

 

Q:	How does the Stellar Board recommend that I vote at the special meeting?

 

A:	The Stellar Board unanimously recommends that you vote:

 

•

“FOR” the merger proposal;

 

•

“FOR” the merger compensation proposal; and

 

•

“FOR” the adjournment proposal.

In considering the recommendations of the Stellar Board, holders of Stellar common stock should be aware that Stellar directors and executive officers may have interests in the merger that are or may be different from, or in addition to, the interests of holders of Stellar common stock generally. For a more complete description of these interests, see the information provided in the section entitled “The Merger—Interests of Stellar’s Directors and Executive Officers in the Merger” beginning on page 80.

 

Q:	Who is entitled to vote at the special meeting?

 

A:

The Stellar Board has fixed the close of business on April 10, 2026 as the record date (the “record date”) for determination of the holders of Stellar common stock entitled to notice of and to vote at the special meeting. Only Stellar shareholders at the close of business on the record date will be entitled to vote at the special meeting. Each holder of Stellar common stock is entitled to cast one (1) vote on each matter properly brought before the special meeting for each share of Stellar common stock that such holder owned of record as of the record date. As of the record date, there were 50,910,698 shares of Stellar common stock outstanding and entitled to be voted at the special meeting. Attendance at the special meeting in person is not required to vote. See below and the section entitled “The Special Meeting—Attending the Special Meeting” beginning on page 45 for instructions on how to vote your shares without attending the special meeting.

 

Q:	What constitutes a quorum for the special meeting?

 

A:

The presence at the special meeting of a majority of the voting power represented by all of the issued and outstanding shares of Stellar common stock entitled to vote at the meeting are present in person or represented by proxy at the meeting will constitute a quorum for the transaction of business at the special meeting. Abstentions will be included in determining the number of shares present at the meeting for the purpose of determining the presence of a quorum.

 

Q:	If my shares of common stock are held in “street name” by my bank, broker, trustee or other nominee, will my bank, broker, trustee or other nominee vote my shares for me?

 

A:

No. If your shares are held in “street name” by a bank, broker, trustee or other nominee, that institution will send you separate instructions describing the procedure for voting your shares. You may not vote shares held in “street name” by returning the proxy directly to Stellar or by voting at the special meeting, unless you provide a “legal proxy,” which you must obtain from your bank, broker, trustee or other nominee.

Banks, brokers, trustees or other nominees who hold shares of Stellar common stock in “street name” for a beneficial owner of those shares typically have the authority to vote in their discretion on “routine”

 

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proposals when they have not received instructions from beneficial owners. However, banks, brokers, trustees or other nominees are not allowed to exercise voting discretion with respect to the approval of matters determined to be “non-routine,” without specific instructions from the beneficial owner. Stellar expects that all proposals to be voted on at the Stellar special meeting will be “non-routine” matters on which banks, brokers, trustees or other nominees do not have discretionary voting power to vote.

If you are a holder of Stellar common stock and you do not instruct your bank, broker or other nominee on how to vote your shares:

 

•

your bank, broker or other nominee may not vote your shares on the merger proposal, which broker non-votes will have the same effect as a vote “AGAINST” the merger proposal (assuming a quorum is present); and

 

•

your bank, broker or other nominee may not vote your shares on the merger compensation proposal and the adjournment proposal, which broker non-votes will have no effect on such proposal (whether or not a quorum is present).

 

Q:	What vote is required for the approval of each proposal at the special meeting?

 

A:	Merger Proposal

Assuming a quorum is present, approval of the merger proposal requires the affirmative vote of the holders of at least two-thirds of the outstanding shares of Stellar common stock entitled to vote thereon at the special meeting. If you mark “ABSTAIN” on your proxy, fail to submit a proxy or vote at the special meeting or fail to instruct your bank, broker, trustee or other nominee how to vote with respect to the merger proposal, it will have the same effect as a vote “AGAINST” the merger proposal.

Merger Compensation Proposal and Adjournment Proposal

Assuming a quorum is present, approval of the merger compensation proposal and adjournment proposal each require the affirmative vote of a majority of the votes cast by holders of Stellar common stock entitled to vote at the special meeting. If you fail to vote, mark “ABSTAIN” on your proxy card or fail to instruct your bank or broker how to vote with respect to any of these proposals, you will be deemed not to have cast a vote with respect to the proposal for which you failed to vote, marked “ABSTAIN” or failed to instruct your bank or broker, and it will have no effect on the proposal.

 

Q:	Why are Stellar shareholders being asked to consider and vote on a proposal to approve, by non-binding, advisory vote, merger-related compensation arrangements for the Stellar named executive officers (i.e., the merger compensation proposal)?

 

A:	Under the SEC rules, Stellar is required to seek an advisory (non-binding) vote with respect to the compensation that may be paid or become payable to Stellar’s named executive officers that is based on or otherwise relates to the merger or “golden parachute” compensation.

 

Q:	What happens if holders of Stellar common stock do not approve the merger compensation proposal?

 

A:

The vote on the merger compensation proposal is separate and apart from the votes to approve the other proposals being presented at the special meeting. Because the vote on the merger compensation proposal is advisory in nature only, it will not be binding upon Stellar, Prosperity or the combined company in the merger. Accordingly, the merger-related compensation will be paid to Stellar’s named executive officers to the extent payable in accordance with the terms of their compensation agreements and other contractual arrangements even if Stellar shareholders do not approve the merger compensation proposal.

 

Q:	How do I submit a proxy or vote my shares at the special meeting?

 

A:	Whether you hold your shares directly as the holder of record of Stellar common stock or beneficially in “street name,” you may direct your vote by proxy without attending the special meeting in person, as applicable.

 

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Record Holders. If you are a holder of record of Stellar common stock, you may vote using any of the following methods:

 

•

By Internet: You can vote by the Internet at www.envisionreports.com/STEL. Have the enclosed proxy card that was provided to you in hand when you access the website and follow the instructions for Internet voting on that website.

 

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By Telephone: You can vote over the telephone by following the instructions on the proxy card.

 

•

By Mail: You may vote by indicating on the proxy card(s) applicable to your Stellar common stock how you want to vote and signing, dating and mailing your proxy card(s) in the enclosed pre-addressed postage-paid envelope as soon as possible to ensure that it will be received in advance of the special meeting. If you are a Stellar shareholder of record and return your signed proxy card but do not indicate your voting preferences, the persons named in the proxy card will vote the shares represented by your proxy card as recommended by the Stellar Board.

 

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At the special meeting: If you are a record holder on the record date, you may vote by proxy or you may attend the special meeting and vote in person.

Stellar must receive your vote no later than the time the polls close for voting at the special meeting for your vote to be counted at the special meeting. Please note that Internet voting and telephone voting will close at 11:59 p.m., Central Time, on May 26, 2026.

Voting your shares by proxy will enable your shares of Stellar common stock to be represented and voted at the special meeting if you do not attend the special meeting and vote your shares in person. By following the voting instructions in the materials you receive, you will direct the designated persons (known as “proxies”) to vote your shares of Stellar common stock at the special meeting in accordance with your instructions. The Stellar Board has appointed Steven F. Retzloff and Robert R. Franklin, Jr. to serve as the proxies for the special meeting. If you vote by the Internet or telephone, you do not have to return your proxy or voting instruction card.

Beneficial Owners. If you own your shares of Stellar common stock beneficially in “street name,” your ability to vote by the Internet or telephone depends on your broker’s voting process. When your shares are held in a brokerage account or by a bank or other nominee, the nominee is considered the record holder of those shares. You are considered the beneficial owner of these shares, and your shares are held in “street name.” This proxy statement/prospectus has been provided to you by your bank, broker, trustee or other nominee. As the beneficial owner, you have the right to direct your nominee concerning how to vote your shares by using the voting instruction card or by following its instructions for voting by the Internet or telephone provided by your nominee.

To vote the shares that you hold in “street name” in person at the special meeting, you must bring a legal proxy from your broker, bank or other nominee, (a) confirming that you were the beneficial owner of those shares as of the close of business on the record date, (b) stating the number of shares of which you were the beneficial owner that were held for your benefit at that time by that broker, bank or other nominee, and (c) appointing you as the record holder’s proxy to vote the shares covered by that proxy at the special meeting. If you fail to bring a nominee-issued proxy to the special meeting, you will not be able to vote your nominee-held shares in person at the special meeting.

Additional information on voting procedures can be found under the section entitled “The Special Meeting” on page 43.

 

Q:	What do I need to do now prior to the special meeting?

 

A:

After carefully reading and considering the information contained in this proxy statement/prospectus, please vote as soon as possible. If you hold shares of Stellar common stock, please respond by completing, signing and dating the accompanying proxy card and returning it in the enclosed postage-paid envelope, or by

 

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submitting your proxy by telephone or through the Internet, as soon as possible so that your shares may be represented at the special meeting. Please note that if you hold shares beneficially in “street name,” you should follow the voting instructions provided by your bank, broker, trustee or other nominee.

 

Q:	Why is my vote important?

 

A:

If you do not vote, it will be more difficult for Stellar to obtain the necessary quorum to hold the special meeting. In addition, your failure to submit a proxy or vote at the special meeting, or failure to instruct your bank, broker, trustee or other nominee how to vote, will have the same effect as a vote “AGAINST” the merger proposal, and an abstention will have the same effect as a vote “AGAINST” the merger proposal. Assuming a quorum is present, approval of the merger proposal requires the affirmative vote of the holders of at least two-thirds of the outstanding shares of Stellar common stock entitled to vote thereon at the special meeting (the “requisite Stellar vote”). The Stellar Board unanimously recommends that you vote “FOR” the merger proposal, “FOR” the merger compensation proposal and “FOR” the adjournment proposal.

 

Q:	What will happen if I return my proxy card without indicating how to vote?

 

A:	If you sign and return your proxy card without indicating how to vote on any particular proposal, the shares of Stellar common stock represented by your proxy will be voted as recommended by the Stellar Board with respect to such proposals.

 

Q:	Can I revoke my proxy or change my vote after I have delivered my proxy or voting instruction card?

 

A:	Yes. Regardless of the method used to cast a vote, if you are the record holder, you may revoke or change your vote by:

 

•

delivering prior to the special meeting a written notice of revocation addressed to: Stellar Bancorp, Inc., 9 Greenway Plaza, Suite 110, Houston, Texas 77046, Attn: Justin M. Long, General Counsel;

 

•

delivering a valid, later-dated proxy, or a later-dated vote by telephone or by the Internet, in a timely manner;

 

•

logging onto the Internet website specified on your proxy card or voting instruction card in the same manner you would to submit your proxy electronically or by calling the telephone number specified on the proxy card or voting instruction card, in each case if you are eligible to do so and following the instructions indicated on the proxy card or voting instruction card; or

 

•

attending the special meeting and voting in person, and any earlier proxy will be revoked. However, attending the special meeting will, by itself, not revoke your proxy.

If you beneficially own your shares in “street name” and you desire to change any voting instructions you have previously given to the record holder of the shares of which you are the beneficial owner, you should contact the bank, broker, trustee or other nominee holding your shares in “street name” in order to direct a change in the manner your shares will be voted.

 

Q:	Will Stellar be required to submit the merger proposal to its shareholders even if the Stellar Board has withdrawn, modified or qualified its recommendation?

 

A:

Yes. Unless the merger agreement is terminated before the special meeting in accordance with its terms, the special meeting will be convened and Stellar is required to submit the merger proposal to its shareholders at the special meeting even if the Stellar Board has withdrawn or modified the Stellar Board recommendation (as defined in the section entitled “The Merger Agreement—Special Meeting and Recommendation of the Stellar Board of Directors”).

 

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Q:	Are there any Stellar shareholders already committed to voting in favor of the merger proposal?

 

A:

Yes. Each of the directors of Stellar who are also shareholders of Stellar, have entered into a voting agreement with Prosperity pursuant to which, among other things, they have agreed to vote in favor of the approval and adoption of the merger agreement, subject to the terms of the voting agreement (the “Stellar voting agreement”). As of the record date for the special meeting, these shareholders collectively and beneficially owned approximately 8.7% of the outstanding shares of Stellar common stock. For information regarding the Stellar voting agreement and certain Stellar shareholders, see the section entitled “The Merger Agreement—Voting Agreements” on page 110.

 

Q:	Are holders of Stellar common stock entitled to appraisal or dissenters’ rights?

 

A:	Yes. Stellar shareholders who vote against the merger proposal, and follow certain procedural steps, will be entitled to dissenters’ rights under the provisions of Chapter 10, Subchapter H of the TBOC.

For more information, see the section entitled “The Merger—Appraisal or Dissenters’ Rights in the Merger” beginning on page 89. In addition, a copy of Chapter 10, Subchapter H of the TBOC is attached as Annex E to this proxy statement/prospectus.

 

Q:	Are there any risks that I should consider in deciding whether to vote for the approval of the merger proposal or the adjournment proposal?

 

A:

Yes. You should read and carefully consider the risk factors set forth in the section entitled “Risk Factors” beginning on page 20. You also should read and carefully consider the risk factors of Prosperity and Stellar contained in the documents that are incorporated by reference into this proxy statement/prospectus.

 

Q:	Does Prosperity pay regular dividends on its shares of common stock?

 

A:

Yes, Prosperity pays quarterly cash dividends on its shares of Prosperity common stock. Prosperity declared quarterly cash dividends on its common stock in 2025, 2024 and 2023. As approved by the Prosperity Board, Prosperity declared and paid a $0.55 per share dividend for the first three fiscal quarters of 2023 and declared and paid a $0.56 per share dividend for the fourth fiscal quarter of 2023. Prosperity declared and paid $0.56 per share dividend for the first three fiscal quarters of 2024 and declared and paid a $0.58 per share dividend for the fourth fiscal quarter of 2024. Prosperity declared and paid a $0.58 per share dividend to holders of Prosperity common stock for the first three fiscal quarters of 2025 and declared and paid a $0.60 per share dividend for the fourth fiscal quarter of 2025. On January 21, 2026, Prosperity announced it has declared a $0.60 per share dividend for the first fiscal quarter of 2026, payable on April 1, 2026, to shareholders of record as of March 13, 2026. The amount of quarterly cash dividends paid on shares of Prosperity common stock is subject to change based on the quarterly dividend amounts approved by the Prosperity Board.

 

Q:	Will Stellar shareholders receive a dividend in respect of shares of Stellar common stock?

 

A:

Each of Stellar and Prosperity has agreed to coordinate with the other on the declaration of any dividends in respect of Stellar common stock and Prosperity common stock and the record dates and payment dates relating thereto. Stellar and Prosperity have further agreed that it is their intention that holders of Stellar common stock will not receive two dividends, or fail to receive one dividend, in any quarter with respect to their shares of Stellar common stock and any shares of Prosperity common stock any such holder receives in exchange therefor in the merger.

 

Q:	What are the material U.S. federal income tax consequences of the merger to U.S. holders of Stellar common stock?

 

A:	The merger is intended to qualify as a “reorganization” (within the meaning of Section 368(a) of the Code) for U.S. federal income tax purposes, and it is a condition to Prosperity’s and Stellar’s respective obligations

 

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to complete the merger that Prosperity and Stellar each receive a tax opinion to the effect that the merger will so qualify. Provided the merger qualifies as a “reorganization” within the meaning of Section 368(a) of the Code, U.S. holders (as defined below) of Stellar common stock generally will recognize gain (but not loss) for U.S. federal income tax purposes on the exchange of their Stellar common stock for Prosperity common stock and cash in the merger in an amount equal to the lesser of: (i) the amount, if any, by which the sum of the cash (excluding cash received in lieu of a fractional share of Prosperity common stock) and the fair market value of the Prosperity common stock received by such U.S. holder in the merger (including any fractional share of Prosperity common stock deemed received and exchanged for cash, as discussed below) exceeds such U.S. holder’s adjusted tax basis in such U.S. holder’s Stellar common stock exchanged therefor and (ii) the amount of cash received by such U.S. holder (excluding cash received in lieu of a fractional share of Prosperity common stock). You should be aware that the U.S. federal income tax consequences to you of the merger may depend upon your own situation. In addition, you may be subject to state, local or non-U.S. tax laws that are not discussed in this proxy statement/prospectus. You should therefore consult with your own tax advisor for a full understanding of the tax consequences to you of the merger. For a more complete discussion of the material U.S. federal income tax consequences of the merger, see the section entitled “Material U.S. Federal Income Tax Consequences of the Merger” beginning on page 112.

 

Q:	When is the merger expected to be completed?

 

A:

Prosperity and Stellar expect to complete the merger in the second quarter of 2026. However, neither Prosperity nor Stellar can predict the actual date on which the merger will be completed, or if the merger will be completed at all, because completion is subject to conditions and factors outside the control of both companies. Before we can complete the merger, Stellar must first obtain the approval of holders of Stellar common stock for the merger, and Prosperity and Stellar must obtain necessary regulatory approvals or waiver of prior approvals and satisfy certain other conditions to completion of the merger.

 

Q:	What are the conditions to completion of the merger?

 

A:

The obligations of Prosperity and Stellar to complete the merger are subject to the satisfaction or waiver of certain closing conditions contained in the merger agreement, including the receipt of required regulatory approvals or waiver of prior approvals and the expiration of statutory waiting periods without the imposition of any materially burdensome regulatory condition (as defined in “The Merger—Regulatory Approvals”), receipt of tax opinions, approval by holders of Stellar common stock of the merger proposal and other customary conditions. For more information, see the section entitled “The Merger Agreement—Conditions to Completion of the Merger” beginning on page 107.

 

Q:	What happens if the merger is not completed?

 

A:

If the merger is not completed, holders of Stellar common stock will not receive any merger consideration for their shares of Stellar common stock in connection with the merger. Instead, Stellar will remain an independent company and Prosperity will not complete the issuance of shares of Prosperity common stock pursuant to the merger agreement. In addition, if the merger agreement is terminated in certain circumstances, a termination fee of $78,000,000 may be payable by Stellar to Prosperity. See the section entitled “The Merger Agreement—Termination Fee” beginning on page 109 for a more detailed discussion of the circumstances under which a termination fee will be required to be paid.

 

Q:	What happens if I sell my shares after the record date but before the special meeting?

 

A:

If you sell or otherwise transfer your shares of Stellar common stock after the record date but before the date of the special meeting, you will retain your right to vote at the special meeting (provided that such shares remain outstanding on the date of the special meeting). In order to receive the merger consideration, you must hold your shares of Stellar common stock through the completion of the merger.

 

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Q:	Should I send in my Stellar common stock certificates now?

 

A:

No. Please do not send in your stock certificates with your proxy. After the merger is completed, an exchange agent designated by Prosperity and reasonably acceptable to Stellar (the “exchange agent”) will send you instructions for exchanging Stellar common stock certificates for the consideration to be received in the merger. See the section entitled “The Merger Agreement—Conversion of Shares; Exchange of Stellar Common Stock Certificates” beginning on page 94.

 

Q:	What should I do if I receive more than one set of voting materials for the same special meeting?

 

A:

You may receive more than one set of voting materials, including multiple copies of this proxy statement and multiple proxy cards or voting instruction cards. For example, if you hold your shares in more than one brokerage account, you will receive a separate voting instruction card for each brokerage account in which you hold shares. Similarly, if you are a shareholder of record and hold shares in a brokerage account, you will receive a proxy card for shares held in your name and a voting instruction card for shares held in “street name.” Please complete, sign, date and return each proxy card and voting instruction card that you receive to ensure that all your shares are voted.

 

Q:	Who can help answer my questions?

 

A:

If you need assistance in completing your proxy card, have questions regarding the special meeting or would like additional copies of this proxy statement/prospectus, please contact Stellar’s Investor Relations at IR@stellar.bank or Stellar’s proxy solicitor, Georgeson LLC, by calling toll-free at (877) 811-4522, or non-toll free at (267) 281-9853.

 

Q:	Where can I find more information about Prosperity and Stellar?

 

A:	You can find more information about Prosperity and Stellar from the various sources described in the section entitled “Where You Can Find More Information” beginning on page 137 of this proxy statement/prospectus.

 

Q:	What is householding and how does it affect me?

 

A:

SEC rules permit Prosperity, Stellar and intermediaries, such as brokers, to satisfy the delivery requirements for proxy materials by delivering a single set of proxy materials to an address shared by two or more of Stellar shareholders, unless contrary instructions have been received in advance according to certain procedures. In cases of such contrary instructions, each shareholder continues to receive a separate notice of the meeting and proxy card.

Certain brokerage firms may have instituted householding for beneficial owners of Stellar common stock held through brokerage firms. If your family has multiple accounts holding Stellar common stock, you may have already received a householding notification from your broker. Please contact your broker directly if you have any questions or require additional copies of this proxy statement/prospectus. The broker will arrange for delivery of a separate copy of this proxy statement/prospectus promptly upon your written or oral request. You may decide at any time to revoke your decision to household, and thereby receive multiple copies.

 

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RISK FACTORS

An investment by Stellar shareholders in Prosperity common stock as a result of the exchange of shares of Prosperity common stock for shares of Stellar common stock in the merger involves certain risks. Certain material risks and uncertainties connected with the merger agreement and transactions contemplated thereby, including the merger and bank merger, and ownership of Prosperity common stock are discussed below. In addition, Prosperity and Stellar discuss certain other material risks connected with the ownership of Prosperity common stock and with Prosperity’s business, and with the ownership of Stellar common stock and Stellar’s business, respectively, under the caption “Risk Factors” appearing in their Annual Reports on Form 10-K most recently filed with the SEC and may include additional or updated disclosures of such material risks in its subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K that each has filed with the SEC or may file with the SEC after the date of this proxy statement/prospectus, each of which reports is or will be incorporated by reference in this proxy statement/prospectus.

Holders of Stellar common stock should carefully read and consider all of these risks and all other information contained in this proxy statement/prospectus, including the discussions of risk factors included in the documents incorporated by reference in this proxy statement/prospectus, in deciding whether to vote for approval of the various proposals for which they may be entitled to vote at the special meeting described herein. The risks described in this proxy statement/prospectus and in those documents incorporated by reference may adversely affect the value of Prosperity common stock that you, as an existing holder of Stellar common stock, will hold upon consummation of the merger, and could result in a significant decline in the value of Prosperity common stock and cause the holders of Stellar common stock to lose all or part of the value of their investments in Prosperity common stock.

Because the market price of Prosperity common stock may fluctuate, holders of Stellar common stock cannot be certain of the market value of the merger consideration they will receive.

In the merger, each share of Stellar common stock issued and outstanding immediately prior to the effective time (excluding dissenting shares, treasury shares and shares held by Stellar or Prosperity (other than treasury shares and shares held by Stellar or Prosperity (i) held in any Stellar benefit plans or related trust accounts, managed accounts, mutual funds and the like, or otherwise held in a fiduciary or agency capacity and (ii) held, directly or indirectly, in respect of debts previously contracted)) will be converted into (a) $11.36 in cash and (b) 0.3803 shares of Prosperity common stock. This exchange ratio is fixed and the stock consideration will not be adjusted for changes in the market price of either Prosperity common stock or Stellar common stock. Changes in the price of Prosperity common stock prior to the merger will affect the value that holders of Stellar common stock will receive in the merger.

Stock price changes may result from a variety of factors, including general market and economic conditions, changes in Prosperity’s or Stellar’s businesses, operations and prospects and regulatory considerations, many of which factors are beyond Prosperity’s or Stellar’s control. Therefore, at the time of the special meeting, holders of Stellar common stock will not know the market value of the Prosperity common stock to be received by holders of Stellar common stock at the effective time. Shareholders of Stellar should obtain current market quotations for shares of Prosperity common stock and for shares of Stellar common stock.

The market price of Prosperity common stock after the merger may be affected by factors different from those currently affecting the shares of Prosperity common stock or Stellar common stock.

Upon completion of the merger, holders of Stellar common stock will become holders of Prosperity common stock. Prosperity’s business differs in important respects from that of Stellar, and, accordingly, the results of operations of Prosperity and the market price of Prosperity common stock after the completion of the merger may be affected by factors different from those currently affecting the independent results of operations of each of Prosperity and Stellar. For a discussion of the businesses of Prosperity and Stellar and of some

 

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important factors to consider in connection with those businesses, see the documents incorporated by reference in this proxy statement/prospectus and referred to under the section entitled “Where You Can Find More Information” beginning on page 137.

Stellar and Prosperity are expected to incur substantial costs related to the merger and integration. If the merger is not completed, Stellar and Prosperity will have incurred substantial expenses without realizing the expected benefits of the merger.

Each of Stellar and Prosperity has incurred and will incur substantial expenses in connection with the negotiation and completion of the transactions contemplated by the merger agreement. These costs include legal, financial advisory, accounting, consulting and other advisory fees, severance/employee benefit-related costs, filing fees and other regulatory fees, printing costs and other related costs. Some of these costs are payable by either Stellar or Prosperity regardless of whether or not the merger is completed. If the merger is not completed, Stellar and Prosperity would have to recognize these expenses without realizing the expected benefits of the merger.

In addition, Prosperity will incur integration costs following the completion of the merger as Prosperity and Stellar integrate their businesses, including facilities and systems consolidation costs and employment-related costs. Stellar may also incur additional costs to maintain employee morale and to retain key employees. There are a large number of processes, policies, procedures, operations, technologies and systems that may need to be integrated, including purchasing, accounting and finance, payroll, compliance, treasury management, branch operations, vendor management, risk management, lines of business, pricing and benefits. While Prosperity and Stellar have assumed that a certain level of costs will be incurred, there are many factors beyond their control that could affect the total amount or the timing of the integration costs. Moreover, many of the costs that will be incurred are, by their nature, difficult to estimate accurately. These integration costs may result in Prosperity taking charges, which may be substantial, against earnings following the completion of the merger, and the amount and timing of such charges are uncertain at present. There can be no assurances that the expected benefits and efficiencies related to the integration of the businesses will be realized to offset these transaction and integration costs over time.

Integrating Stellar’s business into Prosperity may be more difficult, costly or time consuming than expected, and Prosperity may fail to realize the anticipated benefits of the merger.

The success of the merger will depend, in part, on the ability to realize the anticipated synergies and cost savings from combining the businesses of Prosperity and Stellar. To realize the anticipated benefits from the merger, including synergies and cost savings, Prosperity must successfully integrate Stellar into its existing businesses in a manner that permits the anticipated synergies and cost savings to be realized and that does not materially disrupt existing customer relationships or result in decreased revenues due to loss of customers. If Prosperity is not able to successfully achieve these objectives for any reason, including changes in laws or regulations that prevent Prosperity from realizing synergies, the anticipated benefits of the merger may not be realized fully or at all or may take longer to realize than expected. In addition, the actual cost savings of the merger could be less than anticipated, and integration may result in additional and unforeseen expenses. An inability to realize the full extent of the anticipated benefits of the merger and the other transactions contemplated by the merger agreement, as well as any delays encountered in the integration process, could have an adverse effect upon the revenues, levels of expenses and operating results of Prosperity following the completion of the merger, which may adversely affect the value of the stock price of Prosperity following the completion of the merger.

Prosperity and Stellar have operated and, until the completion of the merger, must continue to operate, independently. It is possible that the integration process could result in the loss of key employees, the disruption of each company’s ongoing businesses or inconsistencies in standards, controls, procedures and policies that adversely affect the companies’ ability to maintain relationships with clients, customers, depositors and

 

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employees or to achieve the anticipated benefits of the merger, including synergies and cost savings. Integration efforts between the companies may also divert management attention and resources. These integration matters could have an adverse effect on Prosperity and Stellar during this transition period and on Prosperity for an undetermined period after completion of the merger.

The future results of Prosperity following the completion of the merger may suffer if Prosperity does not effectively manage its expanded operations.

Following the merger, the size and scope of the business of Prosperity will increase beyond the current size and scope of either Prosperity’s or Stellar’s business. Prosperity’s future success following the merger will depend, in part, upon its ability to manage its expanded businesses, which will pose substantial challenges for management, including challenges related to the management and monitoring of new operations and associated increased costs and complexity. There can be no assurances that Prosperity will be successful or that it will realize the expected operating efficiencies, cost savings and other benefits currently anticipated from the merger. In addition, following the merger, Prosperity may be subject to increased scrutiny by, and/or additional regulatory requirements of, governmental authorities as a result of the transaction or the size, scope and complexity of its business operations, which may have an adverse effect on the business, operations or stock price of Prosperity.

Prosperity may be unable to retain Stellar personnel successfully while the merger is pending or after the merger is completed.

The success of the merger and the bank merger will depend in part on Prosperity’s ability to retain the talents and dedication of key employees currently employed by Stellar. It is possible that these employees may decide not to remain with Stellar while the merger is pending or with Prosperity after the merger is completed. If key employees terminate their employment, or if an insufficient number of employees are retained to maintain effective operations, Prosperity’s business activities may be adversely affected and management’s attention may be diverted from successfully integrating Stellar to hiring suitable replacements, all of which may cause Prosperity’s business to suffer. In addition, Prosperity may not be able to locate suitable replacements for any key employees who leave Prosperity, or to offer employment to potential replacements on reasonable terms.

Regulatory approvals may not be received, may take longer than expected or may impose conditions that are not presently anticipated or that could have an adverse effect on Prosperity following the merger.

Before the merger and the bank merger may be completed, various approvals, waivers of prior approvals, consents and non-objections must be obtained from the Federal Reserve Board or the Federal Reserve Bank of Dallas, as applicable, the FDIC and the Texas Department of Banking. In determining whether to grant these approvals, the regulators consider a variety of factors, including the regulatory standing of each party and the factors described under the section entitled “The Merger—Regulatory Approvals” beginning on page 87. These approvals could be delayed or not obtained at all, including due to any or all of the following: an adverse development in either party’s regulatory standing, or any other factors considered by regulators in granting such approvals; governmental, political or community group inquiries, investigations or opposition; or changes in legislation or the political environment. The waiver of prior approval by the Federal Reserve Bank of Dallas was obtained on March 17, 2026.

The approvals that are granted may impose terms and conditions, limitations, obligations or costs, require branch divestitures, or place restrictions on the conduct of Prosperity’s business or require changes to the terms of the transactions contemplated by the merger agreement. There can be no assurance that regulators will not impose any such conditions, limitations, obligations or restrictions or that such conditions, limitations, obligations or restrictions will not have the effect of delaying the completion of any of the transactions contemplated by the merger agreement, imposing additional material costs on or materially limiting the revenues of Prosperity following the merger or will otherwise reduce the anticipated benefits of the merger. In addition,

 

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there can be no assurance that any such conditions, limitations, obligations or restrictions will not result in the delay or abandonment of the merger. Additionally, the completion of the merger is conditioned on the absence of certain orders, injunctions or decrees by any governmental entity of competent jurisdiction that would prohibit or make illegal the completion of any of the transactions contemplated by the merger agreement.

Despite the parties’ commitments to use their reasonable best efforts to promptly prepare and file all necessary documentation in connection with regulatory approvals and cooperate with each other to respond to any request for information and resolve any objection that may be asserted by any governmental entity with respect to the merger agreement, neither Prosperity, Stellar, nor their respective subsidiaries is required under the terms of the merger agreement to take any action, or commit to take any action, or agree to any condition or restriction in connection with obtaining these approvals, that would, individually or in the aggregate, reasonably be likely to have a material adverse effect on the surviving corporation and its subsidiaries, taken as a whole, after giving effect to the merger (and measured on a scale relative to Stellar and its subsidiaries, taken as a whole). See the section entitled “The Merger—Regulatory Approvals” beginning on page 87.

The unaudited pro forma condensed combined financial information included in this proxy statement/prospectus is preliminary and the actual value of the consideration to be issued in the merger as well as the actual financial condition and results of operations of Prosperity after the merger may differ materially.

The unaudited pro forma condensed combined financial information in this proxy statement/prospectus is presented for illustrative purposes only and is not necessarily indicative of what Prosperity’s actual financial condition or results of operations would have been had the merger been completed on the dates indicated. The unaudited pro forma condensed combined financial information reflects adjustments, which are based upon preliminary estimates, to record the Stellar identifiable assets acquired and liabilities assumed at fair value and the resulting goodwill recognized. The fair value estimates reflected in this proxy statement/prospectus are preliminary, and the final amounts will be based upon the actual consideration paid and the fair value of the assets and liabilities of Stellar as of the closing date. Accordingly, (i) the actual value of the consideration paid and the fair value of such assets and liabilities may vary significantly from the value used in preparing the unaudited pro forma combined consolidated financial information in this proxy statement/prospectus, and (ii) the final acquisition accounting adjustments may differ materially from the pro forma adjustments reflected in this proxy statement/prospectus.

The prospective financial information is based on various assumptions and may not be realized.

While presented with numeric specificity, the Prosperity and Stellar prospective financial information provided in this proxy statement/prospectus is based on numerous variables and assumptions (including, but not limited to, those related to the banking, economic, market and financial conditions and additional matters specific to Prosperity’s and Stellar’s businesses, as applicable) that are inherently subjective and uncertain and are outside the control of Prosperity and Stellar. As a result, actual results may differ materially from the prospective financial information. Important factors that may affect actual results and cause the prospective financial information to not be achieved include, but are not limited to, risks and uncertainties relating to Prosperity’s and Stellar’s businesses, as applicable (including each company’s ability to achieve strategic goals, objectives and targets over applicable periods), liabilities that may be greater than anticipated, industry performance, general business and economic conditions. For more information, see the section entitled “The Merger—Certain Unaudited Prospective Financial Information” beginning on page 76.

Certain of Stellar’s directors and executive officers may have interests in the merger that may differ from, or be in addition to, the interests of holders of Stellar common stock generally.

Stellar shareholders should be aware that Stellar directors and executive officers may have interests in the merger and have arrangements that are different from, or in addition to, those of Stellar shareholders. These interests and arrangements may include employment with Prosperity and Prosperity Bank following the

 

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consummation of the merger, appointment as a director of Prosperity or Prosperity Bank, rights to severance, potential vesting of Stellar equity awards, retention awards and rights to ongoing indemnification and insurance coverage, and may create potential conflicts of interest.

The Stellar Board was aware of these interests and considered these interests, among other matters, when making its decision to approve the merger and merger agreement, and in recommending that shareholders approve the merger proposal, the merger compensation proposal and the adjournment proposal. For a more complete description of these interests, please see the section entitled “The Merger—Interests of Stellar’s Directors and Executive Officers in the Merger” beginning on page 80.

If the requisite approval of Stellar shareholders is not obtained, or other conditions to the closing of the merger are not met, the merger agreement may be terminated in accordance with its terms and the merger may not be completed.

The merger agreement is subject to a number of conditions which must be fulfilled in order to complete the merger. Those conditions include: (i) approval of the merger proposal by the requisite Stellar vote; (ii) the shares of Prosperity common stock issuable pursuant to the merger agreement having been authorized for listing on the NYSE, subject to official notice of issuance; (iii) effectiveness of the registration statement on Form S-4 of which this proxy statement/prospectus forms a part; (iv) the absence of any order, injunction or decree issued by any court or governmental entity of competent jurisdiction or other legal restraint or prohibition preventing the consummation of the merger, the bank merger or any of the other transactions contemplated by the merger agreement being in effect, and no law, statute, rule, regulation, order, injunction or decree having been enacted, entered, promulgated or enforced by any governmental entity which prohibits or makes illegal the consummation of the merger, the bank merger or any of the other transactions contemplated by the merger agreement; and (v) all requisite regulatory approvals having been obtained and remaining in full force and effect and all statutory waiting periods in respect thereof having expired, and no such requisite regulatory approval having resulted in the imposition of any materially burdensome regulatory condition. Each party’s obligation to complete the merger is also subject to certain additional customary conditions, including (a) subject to applicable materiality standards, the accuracy of the representations and warranties of the other party; (b) the performance in all material respects by the other party of its obligations under the merger agreement and (c) the receipt by each party of an opinion from its counsel to the effect that the merger will qualify as a “reorganization” within the meaning of Section 368(a) of the Code. See the section entitled “The Merger Agreement—Conditions to Completion of the Merger” beginning on page 107.

Failure to complete the merger could negatively affect Stellar or Prosperity.

The merger agreement is subject to a number of conditions that must be fulfilled in order to complete the merger. Those conditions are described in the section entitled “The Merger Agreement—Conditions to Completion of the Merger” beginning on page 107. These conditions may not be fulfilled in a timely manner or at all, and, accordingly, the merger may be delayed or may not be completed. In addition, if the merger is not completed by January 27, 2027 (which date may be automatically extended to April 27, 2027 in certain circumstances for purposes of obtaining requisite regulatory approvals (as further described in the section entitled “The Merger Agreement—Termination of the Merger Agreement” beginning on page 108)), either Prosperity or Stellar may choose not to proceed with the merger, and the parties can mutually decide to terminate the merger agreement at any time before or after the requisite Stellar shareholder approval.

If the merger is not completed for any reason, there may be various adverse consequences and Prosperity and/or Stellar may experience negative reactions from the financial markets and from their respective customers and employees. For example, Prosperity’s or Stellar’s businesses may have been affected adversely by the failure to pursue other beneficial opportunities due to the focus of management on the merger, without realizing any of the anticipated benefits of completing the merger. Additionally, if the merger agreement is terminated, the market price of Prosperity common stock or Stellar common stock could decline to the extent that the current market

 

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prices reflect a market assumption that the merger will be completed. If the merger agreement is terminated under certain circumstances, Stellar may be required to pay a termination fee of $78,000,000 to Prosperity. See the section entitled “The Merger Agreement—Termination Fee” beginning on page 109. Further, Prosperity and Stellar have incurred and will incur substantial expenses in connection with the negotiation and completion of the transactions contemplated by the merger agreement and those expenses must be paid even if the merger is not completed and neither party realizes the expected benefits of the merger.

Stellar will be subject to business uncertainties and contractual restrictions while the merger is pending.

Uncertainty about the effect of the merger on employees and customers may have an adverse effect on Stellar. These uncertainties may impair Stellar’s ability to attract, retain and motivate key personnel until the merger is completed, and could cause customers and others that deal with Stellar to seek to change existing business relationships with Stellar. In addition, subject to certain exceptions, Stellar has agreed to operate its business in the ordinary course prior to closing, and not to take certain actions which could cause Stellar to be unable to pursue other beneficial opportunities that may arise prior to the completion of the merger. See the section entitled “The Merger Agreement—Covenants and Agreements” beginning on page 97 for a description of the restrictive covenants applicable to Prosperity and Stellar.

In connection with the merger, Prosperity will assume Stellar’s outstanding debt obligations, and Prosperity’s level of indebtedness following the completion of the merger could adversely affect Prosperity’s ability to raise additional capital and to meet its obligations under Stellar’s existing indebtedness following the merger.

In connection with the merger, Prosperity will assume Stellar’s outstanding indebtedness. Stellar’s existing debt, together with any future incurrence of additional indebtedness, could have important consequences for the surviving corporation’s creditors and the surviving corporation’s shareholders. For example, it could limit the surviving corporation’s ability to obtain additional financing for working capital, capital expenditures, debt service requirements, acquisitions and general corporate or other purposes and require a substantial portion of cash flow from operations to be dedicated to the payment of principal and interest on the surviving corporation’s indebtedness, thereby reducing the surviving corporation’s ability to use cash flows to fund its operations, capital expenditures and future business opportunities.

The shares of Prosperity common stock to be received by holders of Stellar common stock as a result of the merger will have different rights from the shares of Stellar common stock.

In the merger, holders of Stellar common stock will become holders of Prosperity common stock and while their rights as shareholders will continue to be governed by Texas law, their rights as shareholders of Prosperity will be governed by the governing documents of Prosperity. The rights associated with Prosperity common stock are different from the rights associated with Stellar common stock. See the section entitled “Comparison of Shareholders’ Rights” beginning on page 120 for a discussion of the different rights associated with Prosperity common stock.

Holders of Stellar common stock will have a reduced ownership and voting interest in Prosperity after the merger and will exercise less influence over management.

Holders of Stellar common stock currently have the right to vote in the election of the board of directors and on other matters affecting Stellar. When the merger is completed, holders of Stellar common stock will become holders of Prosperity common stock, with a percentage ownership of Prosperity that is smaller than the holder’s percentage ownership of Stellar. Based on the number of shares of Prosperity common stock and Stellar common stock outstanding as of April 15, 2026, and based on the number of shares of Prosperity common stock expected to be issued in the merger, the former holders of Stellar common stock, as a group, are estimated to own

 

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approximately 16.1% of the fully diluted shares of Prosperity immediately after the merger and current holders of Prosperity common stock, as a group, are estimated to own approximately 83.9% of the fully diluted shares of Prosperity immediately after the merger. Because of this, holders of Stellar common stock will have less influence on the management and policies of Prosperity than they now have on the management and policies of Stellar.

Holders of Stellar common stock have appraisal rights and dissenters’ rights in the merger.

Appraisal rights (also known as dissenters’ rights) are statutory rights that, if applicable under law, enable shareholders to dissent from an extraordinary transaction, such as a merger, and to demand that the corporation pay the fair value for their shares as determined by a court in a judicial proceeding instead of receiving the consideration offered to shareholders in connection with the extraordinary transaction. If the merger agreement is adopted by Stellar shareholders, Stellar shareholders who vote against the approval of the merger agreement, properly demand payment of the fair value of their shares of Stellar common stock under the applicable provisions of the TBOC and comply with all other applicable requirements of Texas law will be entitled to appraisal rights in connection with the merger under the applicable provisions of the TBOC. Neither Stellar nor Prosperity can predict the number of Stellar shareholders who will seek payment of fair cash value of their shares. See the section entitled “The Merger—Appraisal or Dissenters’ Rights in the Merger” beginning on page 89.

While the merger is pending, Prosperity and Stellar will be subject to business uncertainties and contractual restrictions that could adversely affect each company’s respective business and operations.

Uncertainty about the effect of the transaction on employees, customers, suppliers and other persons with whom Prosperity or Stellar have a business relationship may have an adverse effect on Prosperity’s and Stellar’s respective businesses, operations and stock prices. Existing customers, suppliers and other business partners of Prosperity and Stellar could decide to no longer do business with Prosperity, Stellar or the surviving corporation, reducing the anticipated benefits of the merger. Prosperity and Stellar are also subject to certain restrictions on the conduct of their respective businesses while the merger is pending. As a result, certain other projects may be delayed or abandoned and business decisions could be deferred. In addition, uncertainty may impair Stellar’s ability to attract, retain and motivate key personnel until the merger is completed. If key employees depart because of issues relating to the uncertainty and difficulty of integration or a desire not to remain with Prosperity or Stellar following the merger, the benefits of the merger could be materially diminished.

The merger agreement limits Stellar’s ability to pursue alternatives to the merger and may discourage other companies from trying to acquire Stellar.

The merger agreement contains “no shop” covenants that restrict Stellar’s ability to, directly or indirectly, initiate, solicit, knowingly encourage or knowingly facilitate any inquiries or proposals with respect to, engage or participate in any negotiations with any person concerning, provide any confidential or nonpublic information or data to, or have or participate in any discussions with, any person relating to, any acquisition proposal, subject to certain exceptions, or, during the term of the merger agreement, approve or enter into any term sheet, letter of intent, commitment, memorandum of understanding, agreement in principle, acquisition agreement, merger agreement or other agreement relating to any acquisition proposal (whether written or oral, binding or nonbinding).

The merger agreement further provides that, during the twelve (12)-month period following the termination of the merger agreement under specified circumstances, including the entry into a definitive agreement or consummation of a transaction with respect to an alternative acquisition proposal, Stellar may be required to pay to Prosperity a cash termination fee equal to $78,000,000. See the section entitled “The Merger Agreement—Termination Fee” beginning on page 109.

These provisions could discourage a potential third-party acquirer that might have an interest in acquiring all or a significant portion of Stellar from considering or proposing that acquisition.

 

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The merger agreement subjects Prosperity and Stellar to certain restrictions on their respective business activities prior to the effective time.

The merger agreement subjects Prosperity and Stellar to certain restrictions on their respective business activities prior to the effective time. Subject to certain specified exceptions, the merger agreement obligates Stellar to, and to cause each of its subsidiaries to, (i) conduct its business in the ordinary course in all material respects, (ii) use reasonable best efforts to maintain and preserve intact its business organization and relationships with employees, officers, directors, customers, depositors, suppliers, correspondent banks, governmental entities with jurisdiction over its operations and other third parties having material business relationships with Stellar or any of its subsidiaries and (iii) take no action that would reasonably be likely to adversely affect in any material respect or delay in any material respect the receipt of any necessary approvals of any regulatory agency or other governmental entity required for the transactions contemplated by the merger agreement or to perform its respective covenants and agreements under the merger agreement or to consummate the transactions contemplated by the merger agreement on a timely basis. These restrictions could prevent Prosperity and Stellar from pursuing certain business opportunities that arise prior to the effective time. See the section entitled “The Merger Agreement—Covenants and Agreements—Conduct of Business Prior to the Completion of the Merger” beginning on page 97.

The opinion of Stellar’s financial advisor delivered to the Stellar Board prior to the signing of the merger agreement will not reflect changes in circumstances occurring after the date of such opinion.

The opinion of Stellar’s financial advisor was delivered on, and dated, January 27, 2026. Changes in the operations and prospects of Prosperity and Stellar, general market and economic conditions and other factors which may be beyond the control of Prosperity and Stellar may have altered the value of Prosperity or Stellar or the prices of shares of Prosperity common stock and shares of Stellar common stock as of the date of this proxy statement/prospectus, or may alter such values and prices by the time the merger is completed. The opinion does not speak as of the time the merger will be completed or as of any date other than the date of the opinion. See the section entitled “The Merger—Opinion of Stellar’s Financial Advisor” beginning on page 64.

Issuance of shares of Prosperity common stock in connection with the merger may adversely affect the market price of Prosperity common stock.

In connection with the payment of the merger consideration, Prosperity expects to issue approximately 19,361,338 shares of Prosperity common stock to Stellar shareholders. The issuance of these new shares of Prosperity common stock may result in fluctuations in the market price of Prosperity common stock, including a stock price decrease.

Shareholder litigation related to the merger could prevent or delay the completion of the merger, result in the payment of damages or otherwise negatively impact the business and operations of Prosperity and Stellar.

Shareholders of Prosperity and/or Stellar may file lawsuits against Prosperity, Stellar and/or the directors or officers of either company in connection with the merger. One of the conditions to the closing is that no order, injunction or decree issued by any court or governmental entity of competent jurisdiction or other legal restraint or prohibition preventing the consummation of the merger, the bank merger or any of the other transactions contemplated by the merger agreement be in effect. If any plaintiff were successful in obtaining an injunction prohibiting Prosperity or Stellar defendants from completing the merger, the bank merger or any of the other transactions contemplated by the merger agreement, then such injunction may delay or prevent the consummation of the merger and could result in significant costs to Prosperity and/or Stellar, including any cost associated with the indemnification of directors and officers of each company. Prosperity and Stellar may incur costs in connection with the defense or settlement of any shareholder lawsuits filed in connection with the merger, the bank merger or any other transactions contemplated by the merger agreement. Such litigation could have an adverse effect on the financial condition and results of operations of Prosperity and Stellar and could

 

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prevent or delay the completion of the merger. There has not been any shareholder litigation related to the merger against Prosperity, Stellar or the directors or officers of either company, but such litigation could be instigated.

Risks Relating to Prosperity’s Business

You should read and consider risk factors specific to Prosperity’s business that will also affect Prosperity after the merger. These risks are described in the sections entitled “Risk Factors” in Prosperity’s Annual Report on Form 10-K most recently filed with the SEC and in other documents incorporated by reference into this proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” beginning on page 137 of this proxy statement/prospectus for the location of information incorporated by reference into this proxy statement/prospectus.

Risks Relating to Stellar’s Business

You should read and consider risk factors specific to Stellar’s business that will also affect Stellar after the merger. These risks are described in the sections entitled “Risk Factors” in Stellar’s Annual Report on Form 10-K most recently filed with the SEC and in other documents incorporated by reference into this proxy statement/prospectus. Please see the section entitled “Where You Can Find More Information” beginning on page 137 of this proxy statement/prospectus for the location of information incorporated by reference into this proxy statement/prospectus.

 

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UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

On January 27, 2026, Prosperity and Stellar entered into Agreement and Plan of Merger (as amended from time to time, the “merger agreement”), pursuant to which Stellar will merge with and into Prosperity (the “merger”), with Prosperity as the surviving corporation. Immediately following the merger, Stellar Bank, a wholly owned subsidiary of Stellar, will merge with and into Prosperity Bank, a wholly owned subsidiary of Prosperity, with Prosperity Bank as the surviving bank. In the merger, each holder of shares of Stellar common stock (a “Stellar shareholder”) will receive (i) $11.36 in cash (the “per share cash consideration”) and (ii) 0.3803 shares (the “exchange ratio”) of Prosperity common stock, par value $1.00 per share (“Prosperity common stock”) for each share of Stellar common stock they own as of the effective time of the merger (the consideration described in clauses (i) and (ii) together, the “per share merger consideration” and the aggregate of such consideration, the “merger consideration”).

Prosperity has prepared the unaudited pro forma condensed combined statements of income appearing below to present on a pro forma basis the consolidated statements of income of Prosperity assuming that the merger with Stellar was consummated on January 1, 2025, and to provide information with respect to the pro forma consolidated results of operations that Prosperity would have had for the year ended December 31, 2025. Prosperity has prepared the unaudited pro forma condensed combined balance sheet appearing below to present on a pro forma basis the consolidated financial position of Prosperity assuming that the merger with Stellar was consummated on December 31, 2025. The merger of Prosperity and Stellar will be accounted for as an acquisition of Stellar and Stellar Bank by Prosperity and Prosperity Bank under the acquisition method of accounting in accordance with the Financial Accounting Standard Board’s Accounting Standard Codification Topic 805, Business Combinations (“ASC 805”). The unaudited pro forma condensed combined financial statements of Prosperity and the other pro forma combined financial information appearing below have been prepared using the acquisition method of accounting.

Prosperity’s process of evaluating the significant identifiable long-lived tangible and identifiable intangible assets of Stellar is preliminary. Accordingly, the unaudited pro forma adjustments, including the allocations of the purchase price, are preliminary and have been made solely for the purpose of providing unaudited pro forma condensed combined financial information. Certain reclassifications have been made to the historical financial statements of Stellar to conform to the presentation in Prosperity’s financial statements. Accordingly, the unaudited pro forma condensed combined financial statements and other unaudited pro forma condensed combined financial information are presented for illustrative purposes only and are not necessarily indicative of the results that might have occurred had the merger taken place on January 1, 2025, for statement of income purposes, and on December 31, 2025, for balance sheet purposes. Historical results for any prior period are not necessarily indicative of results to be expected in any future period, and historical results for the year ended December 31, 2025, are not necessarily indicative of results to be expected after the merger. A final determination of the merger consideration and fair values of Stellar’s assets and liabilities, which cannot be made prior to the completion of the merger, will be based on the actual net tangible and intangible assets of Stellar that exist as of the date of completion of the merger. Consequently, amounts preliminarily allocated to goodwill and identifiable intangibles could change significantly from those allocations used in the unaudited pro forma condensed combined financial statements presented below and could result in a material change in amortization of acquired intangible assets.

In connection with the plan to integrate the operations of Prosperity and Stellar following the completion of the merger, Prosperity anticipates that nonrecurring charges, such as costs associated with systems implementation, severance, and other costs related to exit or disposal activities, could be incurred. Prosperity is not able to determine the timing, nature and amount of these charges as of the date of this proxy statement/prospectus. However, these charges could affect the results of operations of Prosperity and Stellar, as well as those of the combined company following the completion of the merger, in the period in which they are recorded. The unaudited pro forma condensed combined financial statements do not include the effects of the costs associated with any restructuring or integration activities resulting from the transaction or any anticipated disposition of assets that may result from such integration.

 

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In addition, future results may differ materially from the results reflected because of various factors, including those discussed in the section entitled “Risk Factors” beginning on page 20. You also should read and carefully consider the risk factors of Prosperity and Stellar contained in the documents that are incorporated by reference into this proxy statement/prospectus, and the factors discussed under the section and “Cautionary Statement Regarding Forward-Looking Statements” beginning on page 39 of this proxy statement/prospectus. Among other factors, the actual amounts recorded as of the completion of the merger may differ materially from the information presented in these unaudited pro forma condensed combined financial statements as a result of:

 

•

changes in the trading price for Prosperity common stock;

 

•

net cash used or generated in Stellar’s operations between the signing of the merger agreement and the completion of the merger; and

 

•

other changes in Stellar’s net assets that occur prior to the completion of the merger, which could cause material differences in the information presented below.

The preparation of the unaudited pro forma condensed combined financial statements and related adjustments required management to make certain assumptions and estimates. The unaudited pro forma condensed combined financial statements should be read together with:

 

•

the accompanying notes to the unaudited pro forma condensed combined financial statements;

 

•

Prosperity’s separate audited historical consolidated financial statements and accompanying notes as of and for the year ended December 31, 2025, included in Prosperity’s Annual Report on Form 10-K for the year ended December 31, 2025; and

 

•

Stellar’s separate audited historical consolidated financial statements and accompanying notes as of and for the year ended December 31, 2025, included in Stellar’s Annual Report on Form 10-K for the year ended December 31, 2025.

The unaudited pro forma condensed combined statements of income for the year ended December 31, 2025 present the consolidated results of operations giving pro forma effect to the following as if they had occurred as of January 1, 2025:

 

•

the full-year impact of Stellar’s statements of income, including pro forma amortization and accretion of purchase accounting adjustments on securities, loans and intangible assets; and

 

•

the issuance of Prosperity common stock, applying the exchange ratio to the shares outstanding of Stellar in determining earnings per share, and the payment of the per share cash consideration.

The unaudited pro forma condensed combined balance sheet as of December 31, 2025 presents the consolidated financial position giving pro forma effect to the following as if they had occurred as of December 31, 2025:

 

•

the completion of the merger, including the issuance of 19,383,615 shares of Prosperity common stock, and the payment of the per share cash consideration (based on the number of shares outstanding of Stellar common stock and other Stellar equity interests as of March 25, 2026 and the exchange ratio); and

 

•

$63.0 million in estimated direct transaction costs related to the merger.

 

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UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET

AS OF DECEMBER 31, 2025

(in thousands)

 

		Prosperity (as reported)				Stellar (as reported)				Reclassifications Note 3				Pro Forma Adjustments				Note 5				Pro Forma Combined
Assets
Cash and due from banks		$	1,747,511			$	419,453			$	—			$	(643,624	)			(a)			$	1,523,340
Federal funds sold			217				—				—				—								217
Total cash and cash equivalents			1,747,728				419,453				—				(643,624	)							1,523,557
Available for sale securities, at fair value			338,197				2,198,459				—												2,536,656
Held to maturity securities, at cost			10,275,228				—				—												10,275,228
Total loans			21,805,368				7,300,591				—				(28,308	)			(b)				29,077,651
Less allowance for credit losses			(333,742	)			(83,629	)			—				(1,971	)			(c)				(419,342	)
Loans, net			21,471,626				7,216,962				—				(30,279	)							28,658,309
Bank premises and equipment, net			383,449				106,118				(15,327	)			—								474,240
Accrued interest receivable			99,297				35,869				—				—								135,166
Goodwill			3,503,127				497,318				—				112,190				(d)				4,112,635
Core deposit intangibles			51,605				71,018				—				88,836				(e)				211,459
Other real estate owned			13,296				7,492				—				—								20,788
Bank Owned Life Insurance (BOLI), net			392,756				109,477				—				—								502,233
Federal Home Loan Bank of Dallas stock			86,950				45,532				—				—								132,482
Other assets			100,166				98,896				15,327				24,444				(f)				238,833
Total assets		$	38,463,425			$	10,806,594			$	—			$	(448,433	)						$	48,821,586
Liabilities and Shareholders’ Equity
Deposits
Noninterest-bearing		$	9,467,911			$	3,407,865			$	—			$	—							$	12,875,776
Interest-bearing			19,014,573				5,613,601				—				—								24,628,174
Total deposits			28,482,484				9,021,466				—				—								37,503,950
Other Borrowings			1,950,000				—				—				—								1,950,000
Securities sold under repurchase agreements			201,216				—				—				—								201,216
Accrued interest payable			30,913				5,508				—				—								36,421
Allowance for credit losses on off-balance sheet credit exposures			37,646				16,204				—				—				(c)				53,850
Other Liabilities			145,026				54,536				—				—								199,562
Subordinated debentures			—				40,226				—				—								40,226
Total liabilities			30,847,285				9,137,940				—				—								39,985,225
Shareholders’ equity:
Total Prosperity equity			7,616,140								—				1,220,221				(g)				8,836,361
Total Stellar equity							1,668,654				—				(1,668,654	)			(g)				—
Total shareholders’ equity			7,616,140				1,668,654				—				(448,433	)			(g)				8,836,361
Total liabilities and shareholders’ equity		$	38,463,425			$	10,806,594			$	—			$	(448,433	)						$	48,821,586

 

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UNAUDITED PRO FORMA CONDENSED COMBINED STATEMENT OF INCOME

FOR THE YEAR ENDED DECEMBER 31, 2025

(in thousands, except per share data)

 

		Prosperity (as reported)					Stellar (as reported)					Reclassifications Note 3					Pro Forma Adjustments					Note 5					Pro Forma Combined
Interest income:
Loans, including fees			$	1,295,474				$	484,877				$	—				$	12,320					(h)				$	1,792,671
Securities				230,696					68,576					—					14,593					(i)					313,865
Federal funds sold and other earning assets				44,153					21,017					—															65,170
Total interest income				1,570,323					574,470					—					26,913										2,171,706
Interest expense:
Deposits				379,977					166,807					—					—										546,784
Other borrowings				104,234					986					—					—										105,220
Securities sold under repurchase agreements				4,620					—					—					—										4,620
Subordinated debentures				—					5,057					—					—										5,057
Total interest expense				488,831					172,850					—					—										661,681
Net interest income				1,081,492					401,620					—					26,913										1,510,025
Provision for credit losses				—					10,158					—					—										10,158
Net interest income after provision for credit losses				1,081,492					391,462					—					26,913										1,499,867
Noninterest income:
Nonsufficient funds (NSF) fees				37,552					—					663					—										38,215
Credit card, debit card and ATM card income				37,408					2,241					1,013					—										40,662
Service charges on deposit accounts				29,988					6,282					(663	)				—										35,607
Trust income				14,648					—					—					—										14,648
Mortgage income				3,859					—					166					—										4,025
Brokerage income				5,385					—					—					—										5,385
Net gain (loss) on sale or write-down of assets				1,217					(302	)				3					—										918
Net gain (loss) on sale or write-up of securities				—					—					(3	)				—										(3	)
Other				38,244					13,569					(1,179	)				—										50,634
Total noninterest income				168,301					21,790					—					—										190,091
Noninterest expense:
Salaries and employee benefits				353,105					168,807					—					—										521,912
Net occupancy and equipment				37,088					17,619					—					—										54,707
Credit and debit card, data processing and software amortization				48,614					22,980					—					—										71,594
Regulatory assessments and FDIC insurance				18,095					6,187					—					—										24,282
Core deposit intangibles amortization				14,442					21,580					—					7,484					(j)					43,506
Depreciation				19,674					8,058					—					—										27,732
Communications				13,988					3,435					—					—										17,423
Net other real estate expense				653					—					1,034					—										1,687
Merger and acquisition expenses				330					—					—					6,000					(k)					6,330
Other				50,224					36,804					(1,034	)				—										85,994
Total noninterest expense				556,213					285,470					—					13,484										855,167
Income before income taxes				693,580					127,782					—					13,429										834,791
Provision for income taxes				150,737					24,910					—					2,820					(l)					178,467
Net income			$	542,843				$	102,872				$	—				$	10,609									$	656,324
Basic earnings per share:
Earnings per share			$	5.72				$	1.99																			$	5.74
Weighted average shares outstanding				94,917					51,756										(32,327	)				(m)					114,346
Diluted earnings per share:
Earnings per share			$	5.72				$	1.99																			$	5.74
Weighted average shares outstanding				94,917					51,808										(32,379	)				(m)					114,346

 

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NOTES TO UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

Note 1. Basis of Pro Forma Presentation

The accompanying unaudited pro forma condensed combined financial statements and related notes were prepared in accordance with Article 11 of Regulation S-X. The unaudited pro forma condensed combined statement of income for the year ended December 31, 2025 combine the historical consolidated statements of income of Prosperity and Stellar giving effect to the merger as if it had been completed on January 1, 2025. The unaudited pro forma condensed combined balance sheet as of December 31, 2025 combines the historical consolidated balance sheets of Prosperity and Stellar giving effect to the merger as if it had been completed on December 31, 2025.

Prosperity’s and Stellar’s historical financial statements were prepared in accordance with U.S. GAAP and presented in U.S. dollars. As discussed in Note 3, Note 4 and Note 5, certain reclassifications were made to align Prosperity’s and Stellar’s financial statement presentation. Prosperity has not identified all adjustments necessary to conform Stellar’s accounting policies to Prosperity’s accounting policies. Upon completion of the merger, or as more information becomes available, Prosperity will perform a more detailed review of Stellar’s accounting policies. As a result of that review, differences could be identified between the accounting policies of the two companies that, when conformed, could have a material impact on the combined company’s financial information.

The accompanying unaudited pro forma condensed combined financial statements and related notes were prepared using the acquisition method of accounting under the provisions of ASC 805, with Prosperity considered the acquirer of Stellar. ASC 805 requires, among other things, that the assets acquired and liabilities assumed in a business combination be recognized at their fair values as of the acquisition date. For purposes of the unaudited pro forma condensed combined balance sheet, the merger consideration has been allocated to the assets acquired and liabilities assumed of Stellar based upon management’s preliminary estimate of their fair values as of December 31, 2025. Prosperity has not completed the valuation analysis and calculations in sufficient detail necessary to arrive at the required estimates of the fair market value of the Stellar’s assets to be acquired or liabilities assumed, other than a preliminary estimate for intangible assets and available for sale securities. Accordingly, apart from the aforementioned, certain Stellar assets and liabilities are presented at their respective carrying amounts and should be treated as preliminary values. Any differences between the fair value of the merger consideration and the fair value of the assets acquired and liabilities assumed will be recorded as goodwill. Accordingly, the purchase price allocation and related adjustments reflected in these unaudited pro forma condensed combined financial statements are preliminary and subject to revision based on a final determination of Stellar’s fair value, which will be based on actual assets and liabilities as of the closing date and cannot be made prior to the completion of the merger. Actual adjustments may differ from the amounts reflected in the unaudited pro forma condensed combined financial information, and the differences may be material.

All dollar amounts presented within these Notes to Unaudited Pro Forma Condensed Combined Financial Statements are in thousands, except per share data. Share amounts are in thousands.

Note 2. Estimated Operational Cost Savings

Prosperity anticipates operational cost savings in connection with the acquisition of Stellar. Prosperity anticipates that these savings will occur through the combination of back office operations and elimination of duplicate general operations, administrative and salary and benefits expense. Estimated cost savings are not presented as part of the pro forma adjustments and there can be no assurance they will be achieved in the amount or manner currently contemplated.

Note 3. Reclassification Adjustments

During the preparation of the unaudited pro forma condensed combined financial information, Prosperity performed a preliminary analysis of Stellar’s financial information to identify differences in accounting policies

 

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and differences in balance sheet and income statement presentation as compared to the presentation of Stellar. At the time of preparing the unaudited pro forma condensed combined financial information, Prosperity had not identified all adjustments necessary to conform Stellar’s accounting policies to Prosperity’s accounting policies and had also not identified all reclassification adjustments necessary to conform Stellar’s financial statement presentation with that of Prosperity’s. The reclassification adjustments represent Prosperity’s best estimates based upon the information currently available to Prosperity and could be materially different from the amounts set forth in the unaudited pro forma condensed combined financial information once more detailed information is available.

Note 4. Preliminary Purchase Price Allocation

The following table summarizes the preliminary purchase price allocation to the estimated fair value of assets and liabilities assumed in the merger:

 

Prosperity shares issued (at exchange ratio of 0.3803) (1)
Prosperity shares issued in exchange for outstanding Stellar common stock (50,913 shares as of March 25, 2026) (2)			19,362
Prosperity shares issued for Stellar options (2)			22
Total Prosperity shares issued			19,384
Pro forma purchase price—Stock (3)			$1,283,221
Cash paid ($11.36 per Stellar share) (1)
Cash paid in exchange for Stellar common stock		$	578,366
Cash paid in exchange for Stellar options (2)			645
Cash paid in exchange for Stellar performance share units (2)			1,613
Pro forma purchase price—Cash		$	580,624
Total pro forma purchase price		$	1,863,845

(1)	Under the terms of the merger agreement, holders of Stellar common stock, options and restricted stock awards will receive 0.3803 shares of Prosperity common stock and $11.36 cash for each share of Stellar common stock (or its equivalent), subject to certain conditions.

(2)	Includes accelerated vesting due to the merger agreement.

(3)	Based upon Prosperity closing price of $66.20 on March 25, 2026.

The preliminary estimated merger consideration as shown in the table above is allocated to the tangible and intangible assets acquired and liabilities assumed of Stellar based on their preliminary estimated fair values. As described above in Note 1, Prosperity has not completed the valuation analysis and calculations in sufficient detail necessary to arrive at the required estimates of the fair market value of the Stellar assets to be acquired or liabilities assumed, other than a preliminary estimate for intangible assets and available for sale securities. Accordingly, apart from the aforementioned, certain assets acquired and liabilities assumed are presented at their respective carrying amounts and should be treated as preliminary values. The fair value assessments are preliminary and are based upon available information and certain assumptions, which Prosperity believes are reasonable under the circumstances. Actual results may differ materially from the assumptions within the unaudited pro forma condensed combined financial statements.

 

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The following table sets forth a preliminary allocation of the estimated merger consideration to the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed of Stellar using Stellar’s consolidated balance sheet as of December 31, 2025:

 

		As of December 31, 2025 (in thousands)
Preliminary fair value of estimated total merger consideration		$	1,863,845
Assets Acquired:
Total cash and cash equivalents		$	419,453
Available for sale securities, at fair value			2,198,459
Loans, net			7,186,683
Bank premises and equipment, net			106,118
Accrued interest receivable			35,869
Core deposit intangibles			159,854
Other real estate owned			7,492
Bank Owned Life Insurance (BOLI), net			109,477
Federal Home Loan Bank of Dallas stock			45,532
Other assets			123,340
Total Assets Acquired		$	10,392,277
Liabilities Assumed:
Deposits-noninterest bearing		$	3,407,865
Deposits-interest bearing			5,613,601
Accrued interest payable			5,508
Allowance for unused commitments			16,204
Other Liabilities			54,536
Subordinated debentures			40,226
Total Liabilities Assumed		$	9,137,940
Net Assets Acquired		$	1,254,337
Preliminary proforma goodwill		$	609,508

Purchase Price Sensitivity

The total pro forma purchase price as shown in the first table of this Note 4 is a preliminary estimate based upon the Prosperity closing price on March 25, 2026 and the number of shares of Stellar common stock (or the equivalent) outstanding as of March 25, 2026. While the per share stock consideration has a fixed exchange ratio of 0.3803 and the per share cash consideration is fixed at $11.36, the aggregate merger consideration will increase or decrease depending on whether the number of shares of Stellar common stock issuable to holders of Stellar options increases or decreases, relative to the amounts shown in the first table of this Note 4 due to fluctuations in the market value of Prosperity common stock. Additionally, the market value of the stock consideration will fluctuate based on fluctuations in the market price of Prosperity common stock. Assuming a 10% change in the market value per share of Prosperity common stock compared to the Prosperity closing price

 

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on March 25, 2026, as shown in the first table of this Note 4, the estimated fair value of the merger consideration transferred would change as shown below.

 

In thousands		10% increase in Prosperity share price				10% decrease in Prosperity share price
Cash portion of estimated purchase price		$	580,860			$	580,405
Stock portion of estimated purchase price			1,411,689				1,154,780
Total estimated purchase price		$	1,992,549			$	1,735,185

Note 5. Pro forma Adjustments and Assumptions

The following pro forma adjustments have been reflected in the unaudited pro forma condensed combined financial information. All adjustments are based on current assumptions and valuations, which are subject to change.

Balance Sheet

 

(a)	This adjustment represents the estimated cash consideration for Stellar and estimated direct transaction costs calculated as follows:

 

Cash paid in exchange for Stellar common stock		$	578,366
Cash paid in exchange for Stellar options			645
Cash paid in exchange for Stellar performance share units			1,613
Total cash consideration ($11.36/share)		$	580,624
Estimated cash paid for direct transaction costs		$	63,000
Pro forma net adjustment to cash and due from bank		$	643,624

 

(b)	Adjustment to total loans to reflect preliminary estimated fair value adjustments on Stellar’s acquired loans.

 

(c)	Adjustment to eliminate Stellar allowance for loan losses and establish Prosperity’s allowance for credit losses on loans.

 

Elimination of Stellar’s allowance for credit losses on loans		$	83,629
Establish Prosperity’s allowance for credit losses on loans			(85,600	)
		$	(1,971	)
Elimination of Stellar’s allowance for credit losses on off-balance sheet credit exposures		$	(16,204	)
Establish Prosperity’s allowance for credit losses on off-balance sheet credit exposures			16,204
		$	—

 

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(d)	Adjustment to goodwill based on the preliminary purchase price allocation as follows:

 

Fair value of merger consideration in excess of the preliminary fair value of net assets acquired (from Note 4 above)		$	609,508
Removal of Stellar historical goodwill			(497,318	)
Pro Forma net adjustment to goodwill		$	112,190

 

(e)	Adjustment to core deposit intangible (“CDI”) based on the preliminary purchase price allocation as follows:

 

Estimated CDI (2% of non-time deposits)		$	159,854
Removal of Stellar historical CDI			(71,018	)
Net Adjustment to CDI		$	88,836

 

(f)	Deferred tax impact from fair value adjustments of $24,444.

 

(g)	Adjustment to Prosperity and Stellar shareholders’ equity based upon the following:

 

Fair value of equity consideration issued to Stellar stockholders (from Note 4 above)		$	1,283,221
Removal of Stellar historical equity			(1,668,654	)
Estimated cash paid for direct transaction costs			(63,000	)
Pro forma net adjustment to shareholders’ equity		$	(448,443	)

Income Statement

 

(h)	Adjustment to interest income on loans for estimated fair value mark on loans amortized over 4 years using the sum of years digits method.

 

(i)	Adjustment to interest income on securities for elimination of Stellar’s net unrealized loss amortized over 5 years using the level yield method.

 

(j)	Estimated core deposit intangible asset amortization at 2.0% of the acquired non-time deposits based upon 10-year life using the sum of years digits amortization method, net of Stellar historical CDI.

 

Estimated CDI (2% of non-time deposits) amortized over 10 years (sum of years digits)		$	29,064
Stellar’s historical CDI Expense			(21,580	)
Estimated net CDI impact		$	7,484

 

(k)	Adjustment to reflect the preliminary estimated one-time merger related expenses, including legal fees and compensation expense.

 

(l)	Adjustment to reflect the net federal income tax effect of the pro forma statement of income adjustments using Prosperity statutory tax rate of 21.0%.

 

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(m)	Adjustment to weighted average shares of Prosperity common stock outstanding to eliminate weighted average shares of Stellar common stock outstanding and to reflect the estimated number of shares issued of Prosperity common stock to holders of Stellar common stock.

 

Adjustments to weighted average number of common shares outstanding—Basic
To reflect acquisition of Stellar basic common shares			(51,756	)
To reflect shares of Prosperity common stock to be issued in the merger			19,384
To reflect shares of Prosperity common stock to be issued after completion of merger			45
			(32,327	)
Adjustments to weighted average number of common shares outstanding—Diluted
To reflect acquisition of Stellar diluted common shares			(51,808	)
To reflect shares of Prosperity common stock to be issued in the merger			19,384
To reflect shares of Prosperity common stock to be issued after completion of merger			45
			(32,379	)

 

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CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

This proxy statement/prospectus contains statements regarding the merger between Prosperity and Stellar; future financial and operating results; benefits and synergies of the merger; future opportunities for the surviving corporation; the issuance of common stock of Prosperity contemplated by the merger agreement; the expected timing of the closing of the merger; the ability of the parties to complete the merger considering the various closing conditions and any other statements about future expectations that constitute forward-looking statements within the meaning of the federal securities laws, including the meaning of the Private Securities Litigation Reform Act of 1995, as amended, Section 27A of the Securities Act, and Section 21E of the Exchange Act. From time to time, oral or written forward-looking statements may also be included in other information released to the public. Such forward-looking statements are typically, but not exclusively, identified by the use in the statements of words or phrases such as “aim,” “anticipate,” “believe,” “estimate,” “expect,” “goal,” “guidance,” “intend,” “is anticipated,” “is expected,” “is intended,” “objective,” “plan,” “projected,” “projection,” “will affect,” “will be,” “will continue,” “will decrease,” “will grow,” “will impact,” “will increase,” “will incur,” “will reduce,” “will remain,” “will result,” “would be,” variations of such words or phrases (including where the word “could,” “may,” or “would” is used rather than the word “will” in a phrase) and similar words and phrases indicating that the statement addresses some future result, occurrence, plan or objective. Forward-looking statements include all statements other than statements of historical fact, including forecasts or trends, and are based on current expectations, assumptions, estimates, and projections about Prosperity and Stellar or related to the merger and are subject to significant risks and uncertainties that could cause actual results to differ materially from the results expressed in such statements.

These forward-looking statements may include information about Prosperity’s and Stellar’s possible or assumed future economic performance or future results of operations, including future revenues, income, expenses, provision for loan losses, provision for taxes, effective tax rate, earnings per share and cash flows and Prosperity’s and Stellar’s future capital expenditures and dividends, future financial condition and changes therein, including changes in Prosperity’s and Stellar’s loan portfolio and allowance for loan losses, future capital structure or changes therein, as well as the plans and objectives of management for Prosperity’s and Stellar’s future operations, future or proposed acquisitions, the future or expected effect of acquisitions on Prosperity’s and Stellar’s operations, results of operations, financial condition, and future economic performance, statements about the anticipated benefits of the proposed transaction, and statements about the assumptions underlying any such statement.

While there is no assurance that any list of risks and uncertainties or risk factors is complete, below are certain factors, in addition to the factors relating to the merger discussed under the caption entitled “Risk Factors” beginning on page 20 and the factors previously disclosed in Prosperity’s and Stellar’s reports filed with the SEC and incorporated by reference into this proxy statement/prospectus, which could cause actual results or performance to differ materially from those contained in or implied by the forward-looking statements:

 

•

the risk that the cost savings and synergies from the merger may not be fully realized or may take longer than anticipated to be realized;

 

•

disruption to Prosperity’s business and to Stellar’s business as a result of the announcement and pendency of the merger;

 

•

the risk that the integration of Stellar’s business and operations into Prosperity, will be materially delayed or will be more costly or difficult than expected, or that Prosperity is otherwise unable to successfully integrate Stellar’s business into its own, including as a result of unexpected factors or events;

 

•

the failure to obtain the necessary approval by the shareholders of Stellar;

 

•

the ability of each of Prosperity and Stellar to obtain required governmental approvals of the merger on the timeline expected, or at all, and the risk that such approvals may result in the imposition of

 

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conditions that could adversely affect Prosperity after the closing of the merger or adversely affect the expected benefits of the merger;

 

•

reputational risk and the reaction of each company’s customers, suppliers, employees or other business partners to the merger;

 

•

the failure of the closing conditions in the merger agreement to be satisfied, or any unexpected delay in closing the merger or the occurrence of any event, change or other circumstances that could give rise to the termination of the merger agreement;

 

•

the possibility that the merger may be more expensive to complete than anticipated, including as a result of unexpected factors or events, diversion of management’s attention from ongoing business operations and opportunities, potential adverse reactions or changes to business or employee relationships, including those resulting from the announcement or completion of the merger, and Prosperity’s ability to complete the acquisition and integration of Stellar successfully;

 

•

the dilution caused by the issuance of additional shares of Prosperity common stock in the merger;

 

•

Prosperity’s revenues after the merger may be less than expected;

 

•

the outcome of any legal or regulatory proceedings that may be currently pending or later instituted against Prosperity before or after the merger, or against Stellar;

 

•

diversion of management’s attention from ongoing business operations;

 

•

general competitive, economic, political and market conditions and other factors that may affect future results of Prosperity and Stellar;

 

•

changes in economic and market conditions that affect the amount and value of the assets of Prosperity Bank and Stellar Bank;

 

•

inaccuracy of the assumptions and estimates that the managements of Prosperity or Stellar make in establishing reserves for probable loan losses and other estimates;

 

•

lack of liquidity, including as a result of a reduction in the amount of sources of liquidity, that Prosperity or Stellar currently have;

 

•

material increases or decreases in the amount of deposits held by Prosperity Bank or Stellar Bank and the cost of those deposits;

 

•

access to the debt and equity markets and the overall cost of funding operations;

 

•

changes in market interest rates that affect the pricing of the loans and deposits of each of Prosperity Bank and Stellar Bank, and the net interest income of each of Prosperity Bank and Stellar Bank;

 

•

fluctuations in the market value and liquidity of the securities Prosperity and Stellar hold for sale, including as a result of changes in market interest rates;

 

•

effects of competition from a wide variety of local, regional, national and other providers of financial, investment and insurance services;

 

•

the occurrence of market conditions adversely affecting the financial industry generally;

 

•

the impact of recent and future legislative and regulatory changes, including changes in banking, securities and tax laws and regulations and their application by Prosperity’s regulators, such as the Dodd-Frank Act, and changes in federal government policies;

 

•

changes in accounting policies and practices, as may be adopted by the bank regulatory agencies, the Financial Accounting Standards Board, the SEC and the Public Company Accounting Oversight Board, as the case may be;

 

•

governmental monetary and fiscal policies, including the policies of the Federal Reserve Board;

 

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•

changes in the scope and cost of FDIC insurance and other coverage;

 

•

changes in inflation;

 

•

an increase in the rate of personal or commercial customers’ bankruptcies;

 

•

technology-related changes may be harder to make or may be more expensive than expected;

 

•

attacks on the security of, and breaches of, Prosperity’s or Stellar’s digital information systems, the costs Prosperity or Stellar incurs to provide security against such attacks and any costs and liability Prosperity or Stellar may incur in connection with any breach of those systems;

 

•

the potential impact of technology and “FinTech” entities and digital currencies on the banking industry generally;

 

•

the impacts related to or resulting from bank failures and other volatility, including potential increased regulatory requirements and costs, such as FDIC special assessments, long-term debt requirements and heightened capital requirements, and potential impacts to macroeconomic conditions, which could affect the ability of depository institutions, including Prosperity and Stellar, to attract and retain depositors and to borrow or raise capital;

 

•

the effects of social media on market perceptions of Prosperity or Stellar and banks generally;

 

•

volatility and disruptions in global capital, foreign exchange and credit markets;

 

•

the ability of the surviving corporation to successfully identify acquisition targets and integrate the businesses of acquired companies and banks;

 

•

the possibility that the surviving corporation will be unable to sustain its current internal growth rate and total growth rate, or achieve its sales objectives;

 

•

the possibility that credit quality could deteriorate;

 

•

the potential changes in customer and consumer demand, including customer and consumer response to marketing;

 

•

the possibility that effectiveness of spending, investments or programs will decline;

 

•

fluctuations in the cost and availability of supply chain resources;

 

•

changes in economic conditions, including currency rate, interest rate and commodity price fluctuations;

 

•

changes in trade policies by the United States or other countries, such as tariffs or retaliatory tariffs;

 

•

the effect, impact, potential duration or other implications of weather and climate-related events; and

 

•

other factors that may affect the future results of Prosperity and Stellar.

Additional factors that could cause results to differ materially from those described above can be found in filings Prosperity and Stellar make with the SEC that are incorporated by reference into this proxy statement/prospectus, as described in the section entitled “Where You Can Find More Information.”

All forward-looking statements are expressly qualified in their entirety by the cautionary statements set forth above. You are cautioned not to place undue reliance on the forward-looking statements, which speak only as of the date of this proxy statement/prospectus or the dates of the documents incorporated by reference in this proxy statement/prospectus and are based on information available at that time. Neither Prosperity nor Stellar assume any obligation to update forward-looking statements to reflect actual results, new information or future events, changes in assumptions or changes in circumstances or other factors affecting forward-looking statements that occur after the date the forward-looking statements were made or to reflect the occurrence of unanticipated events except as required by federal securities laws. If Prosperity or Stellar update one or more forward-looking

 

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statements, no inference should be drawn that Prosperity or Stellar will make additional updates with respect to those or other forward-looking statements. As forward-looking statements involve significant risks and uncertainties, caution should be exercised against placing undue reliance on such statements.

For additional information about factors that could cause actual results to differ materially from those described in the forward-looking statements, please see the reports that Prosperity and Stellar have filed with the SEC as described under the section entitled “Where You Can Find More Information” beginning on page 137.

Prosperity and Stellar expressly qualify in their entirety all forward-looking statements attributable to either of them or any person acting on their behalf by the cautionary statements contained or referred to in this proxy statement/prospectus.

 

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THE SPECIAL MEETING

This section contains information for Stellar shareholders about the special meeting. Stellar is mailing or otherwise delivering this proxy statement/prospectus to you, as a Stellar shareholder, on or about April 23, 2026. This proxy statement/prospectus is also being delivered to Stellar shareholders as Prosperity’s prospectus for its offering of Prosperity common stock in connection with the merger. This proxy statement/prospectus is accompanied by a notice of the special meeting and a proxy that the Stellar Board is soliciting for use by Stellar shareholders at the special meeting and at any adjournments or postponements of the special meeting. References to “you” and “your” in this section are to Stellar shareholders.

Date, Time and Place of the Meeting

The special meeting will be held at its corporate headquarters, which is located at 9 Greenway Plaza, Eighth Floor – Galveston Conference Room, Houston, Texas 77046, on Wednesday, May 27, 2026, 10:00 a.m., Central Time.

Matters to Be Considered

At the special meeting, holders of Stellar common stock will be asked to consider and vote on the following proposals:

 

•

proposal to approve the merger agreement and the transactions contemplated thereby, including the merger (the “merger proposal”);

 

•

proposal to approve, on a non-binding, advisory basis, the compensation that may be paid or become payable to Stellar’s named executive officers that is based on or otherwise relates to the merger (the “merger compensation proposal”); and

 

•

proposal to adjourn or postpone the special meeting, if necessary or appropriate, to solicit additional proxies if, immediately prior to such adjournment or postponement, there are not sufficient votes to approve the merger proposal or to ensure that any supplement or amendment to the accompanying proxy statement/prospectus is timely provided to holders of Stellar common stock (the “adjournment proposal”).

Recommendation of Stellar’s Board of Directors

The Stellar Board has unanimously determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of Stellar and its shareholders and approved and adopted the merger agreement and the transactions contemplated thereby. In reaching the decision to approve and adopt the merger agreement and recommend the approval of the merger to its shareholders, the Stellar Board evaluated the merger and the merger agreement, in consultation with Stellar’s executive management, as well as Stellar’s legal and financial advisors, and considered a number of factors. Accordingly, the Stellar Board unanimously recommends that holders of Stellar common stock vote “FOR” the approval of the merger proposal, “FOR” the merger compensation proposal and “FOR” the adjournment proposal. For a more detailed discussion of the Stellar Board’s recommendation, see the section entitled “The Merger—Stellar’s Reasons for the Merger; Recommendation of the Stellar Board of Directors” beginning on page 61.

Completion of the merger is conditioned upon the approval of the merger proposal, but is not conditioned upon the approval of the merger compensation proposal or the adjournment proposal.

Record Date and Quorum

The Stellar Board has set the close of business on April 10, 2026, as the record date for the special meeting. Only record holders of Stellar common stock at the close of business on April 10, 2026, will be entitled to notice of and to vote at the special meeting and any adjournments or postponements thereof. As of the record date, there were 50,910,698 shares of Stellar common stock outstanding and entitled to vote at the special meeting held by 846 record holders.

 

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The presence at the special meeting of a majority of the voting power represented by all of the issued and outstanding shares of Stellar common stock entitled to vote at the meeting are present in person or represented by proxy at the meeting will constitute a quorum for the transaction of business at the special meeting. Abstentions will be included in determining the number of shares present at the meeting for the purpose of determining the presence of a quorum.

Under the Stellar bylaws, if a quorum is not present at the special meeting, the Stellar shareholders entitled to vote, present in person or represented by proxy, shall have the power to adjourn the meeting, without notice other than announcement at the meeting, until such time and to such place as may be determined by the Stellar Board or by a vote of the holders of a majority of the shares represented in person or by proxy at such meeting until a quorum is present.

At the special meeting, each share of Stellar common stock is entitled to one (1) vote on all matters properly submitted to holders of Stellar common stock.

As of the record date, Stellar directors and executive officers and their affiliates owned and were entitled to vote approximately 4,776,642 shares of Stellar common stock, representing approximately 9.4% of the shares of Stellar common stock outstanding on the record date. Each of Stellar’s directors will vote their shares in favor of the merger proposal and the adjournment proposal, as all are parties to the Stellar voting agreement, a form of which is attached as Annex B to this proxy statement/prospectus and is incorporated by reference herein, pursuant to which they agreed, among other things, to vote in favor of the merger proposal and certain other matters, subject to the terms of such voting agreement. In addition, we currently expect that Stellar’s executive officers will vote their shares in favor of the merger proposal, the merger compensation proposal and the adjournment proposal, although none of them (other than Robert R. Franklin, Jr., who is also a director of Stellar) has entered into any agreements obligating them to do so.

Broker Non-Votes

A broker non-vote occurs when a bank, broker, trustee or other nominee is not permitted to vote on a “non-routine” matter without instructions from the beneficial owner of the shares and the beneficial owner fails to provide the bank, broker, trustee or other nominee with such instructions. Broker non-votes only count toward a quorum if at least one proposal is presented with respect to which the bank, broker, trustee or other nominee has discretionary authority. It is expected that all proposals to be voted on at the special meeting will be “non-routine” matters, and, as such, broker non-votes, if any, will not be counted as present and entitled to vote for purposes of determining a quorum at the special meeting. If your bank, broker, trustee or other nominee holds your shares of Stellar common stock in “street name,” such entity will vote your shares of Stellar common stock only if you provide instructions on how to vote by complying with the voter instruction form sent to you by your bank, broker, trustee or other nominee with this proxy statement/prospectus.

Vote Required; Treatment of Abstentions; Broker Non-Votes and Failure to Vote

Merger proposal:

 

•

Vote required: Assuming a quorum is present, approval of the merger proposal requires the affirmative vote of the holders of at least two-thirds of the outstanding shares of Stellar common stock entitled to vote thereon at the special meeting.

 

•

Effect of abstentions and broker non-votes: If you mark “ABSTAIN” on your proxy, fail to submit a proxy or vote at the special meeting or fail to instruct your bank, broker, trustee or other nominee how to vote with respect to the merger proposal, it will have the same effect as a vote “AGAINST” the merger proposal.

 

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Merger compensation proposal:

 

•

Vote required: Assuming a quorum is present, approval of the merger compensation proposal requires the affirmative vote of a majority of the votes cast by holders of Stellar common stock entitled to vote at the special meeting. Approval of the merger compensation proposal is not a condition to the completion of the merger. If the merger is completed, the merger-related compensation will be paid to Stellar’s named executive officers to the extent payable in accordance with the terms of the compensation agreements and arrangements even if holders of Stellar common stock fail to approve the advisory (non-binding) proposal regarding the merger-related compensation.

 

•

Effect of abstentions and broker non-votes: If you mark “ABSTAIN” on your proxy, fail to submit a proxy or vote at the special meeting or fail to instruct your bank, broker, trustee or other nominee how to vote with respect to the merger compensation proposal, your shares will not be deemed to be a vote cast at the special meeting and it will have no effect on the merger-compensation proposal.

Adjournment proposal:

 

•

Vote required: Assuming a quorum is present, approval of the adjournment proposal requires the affirmative vote of a majority of the votes cast by holders of Stellar common stock entitled to vote at the special meeting. Approval of the adjournment proposal is not a condition to the completion of the merger.

 

•

Effect of abstentions and broker non-votes: If you mark “ABSTAIN” on your proxy, fail to submit a proxy or vote at the special meeting or fail to instruct your bank, broker, trustee or other nominee how to vote with respect to the adjournment proposal, your shares will not be deemed to be a vote cast at the special meeting and it will have no effect on the adjournment proposal.

Attending the Special Meeting

If you are a holder of record of Stellar common stock on the record date, you will be able to attend and vote at the special meeting and vote during the meeting. Each person attending the special meeting must present a valid, government-issued form of identification in order to be admitted to the special meeting. Each shareholder attending also must provide proof of ownership of shares of Stellar common stock as of the record date. If you are a record holder, proof of ownership will be established by Stellar’s verification of your name against Stellar’s list of record holders as of the record date.

If you hold Stellar common stock through a broker, bank, trustee or other nominee, you must bring a copy of a statement reflecting your stock ownership as of the record date, and if you wish to vote in person, you must also bring a legal proxy from your bank, broker, trustee or other nominee. See the section entitled “—Shares Held in Street Name” below for further information. Due to space limitations, attendance is limited to shareholders and persons holding valid legal proxies from those shareholders. Admission to the special meeting is on a first-come, first-served basis.

If you hold your shares through a bank, broker, trustee or other nominee and you do not want to attend the special meeting, please contact the respective entity for instructions on how to vote your shares of Stellar common stock at the special meeting. Cameras, recording devices, and other electronic devices are not permitted.

Even if you plan to attend the special meeting, Stellar recommends that you vote your shares in advance by proxy as described below so that your vote will be counted if you later decide not to or become unable to attend the special meeting.

Proxies

Voting your shares by proxy will enable your shares of Stellar common stock to be represented and voted at the special meeting if you do not attend the special meeting and vote your shares in person. By following the

 

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voting instructions in the materials you receive, you will direct the designated persons (known as “proxies”) to vote your shares of Stellar common stock at the special meeting in accordance with your instructions. The Stellar Board has appointed Steven F. Retzloff and Robert R. Franklin, Jr. to serve as the proxies for the special meeting. If you vote by the Internet or telephone, you do not have to return your proxy or voting instruction card.

If you hold your shares of Stellar common stock in your name as a holder of record, to submit a proxy, you, as a holder of Stellar common stock, may use one of the following methods:

 

•

By Internet: You can vote by the Internet at www.envisionreports.com/STEL. Have the enclosed proxy card that was provided to you in hand when you access the website and follow the instructions for Internet voting on that website.

 

•

By Telephone: You can vote over the telephone by following the instructions on the proxy card.

 

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By Mail: You may vote by indicating on the proxy card(s) applicable to your Stellar common stock how you want to vote and signing, dating and mailing your proxy card(s) in the enclosed pre-addressed postage-paid envelope as soon as possible to ensure that it will be received in advance of the special meeting. If you are a Stellar shareholder of record and return your signed proxy card but do not indicate your voting preferences, the persons named in the proxy card will vote the shares represented by your proxy card as recommended by the Stellar Board.

Stellar requests that holders of Stellar common stock vote by telephone, over the Internet or by completing and signing the accompanying proxy card and returning it to Stellar as soon as possible in the enclosed postage-paid envelope. When the accompanying proxy card is returned properly executed, the shares of Stellar common stock represented by it will be voted at the special meeting in accordance with the instructions contained on the proxy card. If you make no specification on your proxy card as to how you want your shares voted before signing and returning it, your proxy will be voted “FOR” the merger proposal, “FOR” the merger compensation proposal and “FOR” the adjournment proposal.

If a holder’s shares are held in “street name” by a bank, broker, trustee or other nominee, the holder should check the voting form used by that firm to determine whether the holder may vote by telephone or the Internet.

Every vote is important. Accordingly, you should sign, date and return the enclosed proxy card, or vote via the Internet or by telephone, whether or not you plan to attend the special meeting. Sending in your proxy card or voting by telephone or on the Internet will not prevent you from voting your shares personally through attendance at the special meeting because you may subsequently revoke your proxy.

Shares Held in Street Name

If your shares are held in “street name” through a bank, broker, trustee or other nominee, you must instruct the broker, bank or other nominee on how to vote your shares. Your bank, broker, trustee or other nominee will vote your shares only if you provide specific instructions on how to vote by following the instructions provided to you by your broker, bank or other nominee.

To vote the shares that you hold in “street name” in person at the special meeting, you must bring a legal proxy from your broker, bank or other nominee, (1) confirming that you were the beneficial owner of those shares as of the close of business on the record date, (2) stating the number of shares of which you were the beneficial owner that were held for your benefit at that time by that broker, bank or other nominee, and (3) appointing you as the record holder’s proxy to vote the shares covered by that proxy at the special meeting. If you fail to bring a nominee-issued proxy to the special meeting, you will not be able to vote your nominee-held shares in person at the special meeting.

Further, banks, brokers, trustees or other nominees who hold shares of Stellar common stock on behalf of their customers may not give a proxy to Stellar to vote those shares with respect to any non-routine matters without specific instructions from you, as banks, brokers, trustees and other nominees do not have discretionary

 

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voting power on any non-routine matters that will be voted upon at the special meeting, including the merger proposal, the merger compensation proposal and the adjournment proposal.

Revocability of Proxies

If you are a holder of Stellar common stock of record, you may revoke your proxy at any time before it is voted by:

 

•

completing, signing, dating and returning a proxy card with a later date;

 

•

delivering a duly executed written revocation letter to Stellar’s corporate secretary;

 

•

attending the special meeting, notifying the corporate secretary and voting by ballot at the special meeting; or

 

•

voting by telephone or the Internet at a later time (but prior to 11:59 p.m. Central Time on the day before the special meeting).

If you hold your shares of Stellar common stock through a bank, broker, trustee or other nominee, you should contact your bank, broker, trustee or other nominee to change your vote.

Attending the special meeting without voting in person will not revoke your proxy. A revocation or later-dated proxy received by Stellar after the vote will not affect the vote. Written notices of revocation and other communications about revoking your proxy card should be addressed to:

Stellar Bancorp, Inc.

9 Greenway Plaza, Suite 110

Houston, Texas 77046

Attention: Corporate Secretary

If your shares are held in “street name” by a bank, broker or other nominee, you should follow the instructions of your bank, broker or other nominee regarding the revocation of proxies.

If the special meeting is postponed or adjourned, it will not affect the ability of holders of Stellar common stock of record as of the record date to exercise their voting rights or to revoke any previously granted proxy using the methods described above.

Delivery of Proxy Materials

As permitted by applicable law, only one (1) copy of this proxy statement/prospectus is being delivered to holders of Stellar common stock residing at the same address, unless such holders of Stellar common stock have notified Stellar of their desire to receive multiple copies of the proxy statement/prospectus.

Stellar will promptly deliver, upon oral or written request, a separate copy of the proxy statement/prospectus to any holder of Stellar common stock residing at an address to which only one (1) copy of such document was mailed. Requests for additional copies should be directed to Stellar’s Investor Relations at IR@stellar.bank or Stellar’s proxy solicitor, Georgeson LLC, by calling toll-free at (877) 811-4522, or non-toll free at (267) 281-9853.

Solicitation of Proxies

Prosperity and Stellar will share equally the expenses incurred in connection with the printing and mailing of this proxy statement/prospectus. To assist in the solicitation of proxies, Stellar has retained Georgeson LLC, for a fee of $21,000 plus the cost of additional services to be agreed and expenses. Stellar and its proxy solicitor will also request banks, brokers, trustees and other intermediaries holding shares of Stellar common stock beneficially owned by others to send this document to, and obtain proxies from, the beneficial owners and may

 

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reimburse such record holders for their reasonable out-of-pocket expenses in so doing. Solicitation of proxies by mail may be supplemented by telephone and other electronic means, advertisements and personal solicitation by the directors, officers or employees of Stellar. No additional compensation will be paid to Stellar’s directors, officers or employees for solicitation.

You should not send in any Stellar stock certificates with your proxy card (or, if you hold your shares in “street name” your voting instruction card). The exchange agent will mail a transmittal letter with instructions for the surrender of stock certificates to holders of Stellar common stock as soon as practicable after completion of the merger.

Other Matters to Come Before the Special Meeting

Stellar management knows of no other business to be presented at the special meeting, but if any other matters are properly presented to the meeting or any adjournments thereof, the persons named in the proxies will vote upon them in accordance with the Stellar Board’s recommendations.

Assistance

If you need assistance in completing your proxy card, have questions regarding the special meeting or would like additional copies of this proxy statement/prospectus, please contact Stellar’s Investor Relations at IR@stellar.bank or Stellar’s proxy solicitor, Georgeson LLC, by calling toll-free at (877) 811-4522, or non-toll free at (267) 281-9853.

 

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STELLAR PROPOSALS

Proposal 1: Merger Proposal

Stellar is asking holders of Stellar common stock to approve the merger agreement and approve the transactions contemplated thereby, including the merger. Holders of Stellar common stock should read this proxy statement/prospectus carefully and in its entirety, including the annexes, for more detailed information concerning the merger agreement and the merger. A copy of the merger agreement is attached to this proxy statement/prospectus as Annex A.

After careful consideration, the Stellar Board unanimously determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of Stellar and its shareholders and approved and adopted the merger agreement and the transactions contemplated thereby. See the section entitled “The Merger—Stellar’s Reasons for the Merger; Recommendation of the Stellar Board of Directors” beginning on page 61 for a more detailed discussion of the Stellar Board’s recommendation.

The approval of the merger proposal by Stellar shareholders is a condition to the completion of the merger.

The Stellar Board unanimously recommends a vote “FOR” the merger proposal.

 

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Proposal 2: Merger Compensation Proposal

Pursuant to Section 14A of the Exchange Act and Rule 14a-21(c) thereunder, Stellar is seeking a non-binding, advisory shareholder approval of the compensation of Stellar’s named executive officers that is based on or otherwise relates to the merger as disclosed in the section entitled “The Merger—Merger-Related Compensation for Stellar’s Named Executive Officers” beginning on page 84. The proposal gives holders of Stellar common stock the opportunity to express their views on the merger-related compensation of Stellar’s named executive officers.

Accordingly, Stellar is asking holders of Stellar common stock to vote “FOR” the adoption of the following resolution, on an advisory (non-binding) basis:

“RESOLVED, that the compensation that will or may be paid or become payable to the Stellar named executive officers, in connection with the merger, and the agreements or understandings pursuant to which such compensation will or may be paid or become payable, in each case as disclosed pursuant to Item 402(t) of Regulation S-K in “The Merger—Merger-Related Compensation for Stellar’s Named Executive Officers” are hereby APPROVED.”

The vote on the merger compensation proposal is a vote separate and apart from the votes on the merger proposal and the adjournment proposal. Accordingly, if you are a holder of Stellar common stock, you may vote to approve the merger proposal and the adjournment proposal, and vote not to approve the merger compensation proposal, and vice versa. The approval of the merger compensation proposal by holders of Stellar common stock is not a condition to the completion of the merger. If the merger is completed, the merger-related compensation will be paid to Stellar’s named executive officers to the extent payable in accordance with the terms of the compensation agreements and arrangements even if holders of Stellar common stock fail to approve the advisory (non-binding) vote regarding merger-related compensation.

The Stellar Board unanimously recommends a vote “FOR” the merger compensation proposal.

 

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Proposal 3: Adjournment Proposal

The special meeting may be adjourned to another time or place, if necessary or appropriate, to solicit additional proxies if there are insufficient votes at the time of the special meeting to approve the merger proposal or to ensure that any supplement or amendment to this proxy statement/prospectus is timely provided to holders of Stellar common stock.

If, at the special meeting, the number of shares of Stellar common stock present or represented and voting in favor of the merger proposal is insufficient to approve the merger proposal, Stellar intends to move to adjourn the special meeting in order to enable the Stellar Board to solicit additional proxies for approval of the merger proposal. In that event, Stellar will ask holders of Stellar common stock to vote upon the adjournment proposal, but not the merger proposal or the merger compensation proposal.

In this proposal, Stellar is asking holders of Stellar common stock to authorize the holder of any proxy solicited by the Stellar Board, on a discretionary basis, to vote in favor of adjourning the special meeting to another time and place for the purpose of soliciting additional proxies, including the solicitation of proxies from holders of Stellar common stock who have previously voted. If the date of the adjournment is not announced at the special meeting or a new record date is fixed for the adjourned meeting, a new notice of the adjourned meeting will be given to each shareholder of record entitled to vote at the adjourned meeting.

The approval of the adjournment proposal by holders of Stellar common stock is not a condition to the completion of the merger.

The Stellar Board recommends a vote “FOR” the adjournment proposal.

 

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INFORMATION ABOUT PROSPERITY

Prosperity Bancshares, Inc.

Prosperity Bank Plaza

4295 San Felipe

Houston, Texas 77027

(281) 269-7199

Prosperity Bancshares, Inc. was formed in 1983 as a vehicle to acquire the former Allied Bank in Edna, Texas, which was chartered in 1949 as The First National Bank of Edna and is now known as Prosperity Bank. Prosperity is a Texas corporation and a registered financial holding company that derives substantially all of its revenues and income from the operation of its bank subsidiary, Prosperity Bank. Prosperity Bank provides a wide array of financial products and services to businesses and consumers throughout Texas and Oklahoma. As of February 1, 2026, Prosperity Bank operated 312 full service banking locations: 62 in the Houston area, including The Woodlands; 36 in the South Texas area including Corpus Christi and Victoria; 61 in the Dallas/Fort Worth area; 22 in the East Texas area; 28 in the Central Texas area including Austin and San Antonio; 45 in the West Texas area including Lubbock, Midland-Odessa, Abilene, Amarillo and Wichita Falls; 15 in the Bryan/College Station area; 6 in the Central Oklahoma area; 8 in the Tulsa, Oklahoma area; 18 in the Central, South Texas and San Antonio areas currently doing business as American Bank; and 11 in the Central Texas area, including San Antonio and the Hill County, currently doing business as Texas Partners Bank. Effective January 1, 2026, Prosperity completed its previously announced acquisition of American Bank Holding Corporation, a Texas corporation headquartered in Corpus Christi, Texas. Additionally, effective February 1, 2026, Prosperity completed its previously announced acquisition of Southwest Bancshares, Inc., a Texas corporation headquartered in San Antonio, Texas.

As of December 31, 2025, Prosperity had total assets of $38.46 billion, total loans of $21.81 billion, total deposits of $28.48 billion and total shareholders’ equity of $7.62 billion.

Prosperity common stock is traded on the NYSE under the symbol “PB.”

Prosperity’s principal executive office is located at Prosperity Bank Plaza, 4295 San Felipe in Houston, Texas and its telephone number at that location is (281) 269-7199. Prosperity’s website is https://www.prosperitybankusa.com/. The information on Prosperity’s website is not part of this proxy statement/prospectus, and the references to the Prosperity website address do not constitute incorporation by reference of any information on that website into this proxy statement/prospectus.

Additional information about Prosperity and its subsidiaries is included in documents incorporated by reference in this proxy statement/prospectus. See the section entitled “Where You Can Find More Information” beginning on page 137.

 

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INFORMATION ABOUT STELLAR

Stellar Bancorp, Inc.

9 Greenway Plaza, Suite 110

Houston, Texas 77046

(713) 210-7600

Stellar is a Texas corporation and registered bank holding company headquartered in Houston, Texas. Through its wholly owned bank subsidiary, Stellar Bank, a Texas state-chartered member bank with its main office in Houston, Texas, Stellar provides a diversified range of commercial banking services primarily to small-to medium-sized businesses, professionals and individual customers within its markets. As of December 31, 2025, Stellar Bank operated 52 banking centers, with 35 banking centers located in the Houston metropolitan area, 16 banking centers located in the Beaumont metropolitan area, and one banking center in Dallas, Texas.

As of December 31, 2025, Stellar had total assets of $10.81 billion, total loans of $7.30 billion, total deposits of $9.02 billion and total shareholders’ equity of $1.67 billion.

Stellar common stock is traded on the NYSE under the symbol “STEL.”

Stellar’s principal office is located at 9 Greenway Plaza, Suite 110, Houston, Texas 77046, and its telephone number at that location is (713) 210-7600. Additional information about Stellar and its subsidiaries is included in documents incorporated by reference in this proxy statement/prospectus. See the section entitled “Where You Can Find More Information” beginning on page 137.

 

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THE MERGER

This section of the proxy statement/prospectus describes material aspects of the merger. This summary may not contain all of the information that is important to you. You should carefully read this entire proxy statement/prospectus and the other documents we refer you to for a more complete understanding of the merger. In addition, we incorporate important business and financial information about Prosperity and Stellar into this proxy statement/prospectus by reference. You may obtain the information incorporated by reference into this proxy statement/prospectus without charge by following the instructions in the section entitled “Where You Can Find More Information” beginning on page 137.

Terms of the Merger

Each of Prosperity’s and Stellar’s respective board of directors has approved the merger agreement. The merger agreement provides that Stellar will merge with and into Prosperity, with Prosperity as the surviving corporation. Following the completion of the merger, Stellar Bank, a Texas banking association and a wholly owned bank subsidiary of Stellar, will merge with and into Prosperity Bank, a Texas banking association and a wholly owned bank subsidiary of Prosperity, with Prosperity Bank as the surviving bank.

Under the terms and subject to the conditions set forth in the merger agreement, holders of Stellar common stock will receive (i) $11.36 in cash (the “per share cash consideration”) and (ii) 0.3803 shares (the “exchange ratio”) of Prosperity common stock (the consideration described in clauses (i) and (ii), the “per share merger consideration” and the aggregate of such consideration, the “merger consideration”) for each share of Stellar common stock issued and outstanding immediately prior to the effective time of the merger (excluding dissenting shares, treasury shares and shares held by Stellar or Prosperity (other than treasury shares and shares held by Stellar or Prosperity (a) held in any Stellar benefit plans or related trust accounts, managed accounts, mutual funds and the like, or otherwise held in a fiduciary or agency capacity and (b) held, directly or indirectly, in respect of debts previously contracted)).

If the aggregate number of shares of Prosperity common stock to be issued in connection with the merger agreement (the “aggregate stock consideration”) would exceed nineteen and nine-tenths of a percent (19.9%) of the issued and outstanding shares of Prosperity common stock immediately prior to the effective time of the merger (the “Prosperity stock consideration cap”), (i) the exchange ratio will be reduced to the minimum extent necessary (rounded down to the nearest ten-thousandth when expressed in decimal form) such that the aggregate stock consideration does not exceed the Prosperity stock consideration cap and (ii) the per share cash consideration will be increased (for the avoidance of doubt, on a per share basis) by an amount in cash equal to the Prosperity share closing price multiplied by the difference between the initial exchange ratio and the exchange ratio as reduced (rounded down to the nearest whole cent). Prosperity will not issue any fractional shares of Prosperity common stock in the merger. Holders of Stellar common stock who would otherwise be entitled to a fraction of a share of Prosperity common stock in the merger will instead receive, for the fraction of a share, an amount in cash (rounded to the nearest cent), without interest, equal to (i) such fractional part of a share of Prosperity common stock (after taking into account all of the shares of Stellar common stock held by such holder immediately prior to the effective time of the merger and rounded to the nearest thousandth when expressed in decimal form) multiplied by (ii) the Prosperity share closing price.

Holders of Stellar common stock are being asked to approve the merger and the merger agreement. See the section entitled “The Merger Agreement” beginning on page 92 for additional and more detailed information regarding the legal documents that govern the merger, including information about the conditions to the completion of the merger and the provisions for terminating or amending the merger agreement.

Background of the Merger

As part of the ongoing consideration and evaluation of their respective long-term prospects and strategies, each of the Prosperity Board and the Stellar Board and Prosperity’s and Stellar’s senior management have

 

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regularly reviewed and assessed their respective business strategies and objectives, including assessments of strategic growth opportunities potentially available to Prosperity and Stellar, as part of their respective continuous efforts to enhance value for their respective shareholders and deliver the best possible services to their respective customers and communities. These reviews have focused on, among other things, prospects and developments in the financial services industry, the regulatory environment, the economy generally, and financial markets, and the implications of such developments for financial institutions generally and Prosperity and Stellar, in particular. These reviews have also included assessments of ongoing consolidation in the financial services industry and the benefits and risks to Prosperity and Stellar, respectively, and their respective shareholders, of strategic combinations compared to the benefits and risks of continued operation as a stand-alone company.

During the second quarter of 2025, Stellar pursued a potential business combination as an acquirer and submitted a letter of intent to acquire another Texas financial institution (“Company A”) in an all-stock transaction. Stellar was notified by Company A’s financial advisor that Company A would pursue a transaction with a different potential acquirer, as that acquirer proposed a premium to Stellar’s proposal.

At regular meetings of the Stellar Board and Board of Directors of Stellar Bank (the “Bank Board”) held on August 27, 2025, Mr. Robert F. Franklin, Jr., Stellar’s Chief Executive Officer, discussed the outcome of the proposal to acquire Company A and strategic alternatives available to Stellar as well as current and expected market conditions and the overall regulatory environment.

On September 19, 2025, Stellar held a joint board retreat with members of the Stellar Board and the Bank Board to discuss the operations of the Bank including growth initiatives and strategic alternatives that would create shareholder value as part of its strategic planning process. In connection with its review, the Stellar Board invited an investment bank to make a presentation to the Stellar Board regarding various strategic alternatives that the Bank might pursue, including analysis and evaluation of the markets for financial institutions, selected stand-alone initiatives along with potential merger and acquisition scenarios, each intended to maximize shareholder value. The Stellar Board met and discussed strategic alternatives, and that it would be in the best interests of Stellar and its shareholders to explore a potential business combination transaction, including a potential acquisition of Stellar by a larger financial institution. The Stellar Board also discussed how to confidentially assess potential partners for a possible combination transaction. The Stellar Board authorized Mr. Franklin to engage in discussions with a financial advisor regarding potential transaction partners.

On September 22, 2025, Mr. Franklin engaged in discussions with representatives of Keefe, Bruyette & Woods, Inc., a Stifel company (“KBW”), assisting Stellar with identifying and assessing potential partners for a possible business combination transaction with Stellar. Over the next few days, Mr. Franklin and the KBW representatives discussed certain financial institutions with potential interest in a business combination transaction with Stellar, including their apparent financial capacity to acquire Stellar. Following such discussions, Stellar instructed KBW as its financial advisor to contact nine potential partners who might have an interest and a capacity to acquire Stellar. Over the following few days, in accordance with Stellar’s directives, KBW individually contacted the nine potential partners on a no-names basis regarding each party’s potential interest in discussing a possible business combination transaction.

From time to time, Mr. Franklin has met with executive officers of other financial institutions to have general discussions about the banking industry, including at industry and investor conferences. Prior to the discussions with KBW, Mr. Franklin had scheduled a lunch meeting with the Chief Operating Officer of a publicly traded regional bank holding company (“Company B”) to take place on September 23, 2025. Company B was contacted by KBW in advance of the lunch meeting and expressed interest in a potential business combination. On September 23, 2025, Mr. Franklin met with the Chief Executive Officer of Company B for lunch. On September 26, 2025, Stellar and Company B executed a non-disclosure agreement to permit further discussions about a potential business combination.

 

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On October 1, 2025, Stellar executed a non-disclosure agreement with a publicly traded regional bank holding company (“Company C”), which KBW had contacted, in advance of a meeting between Mr. Franklin and Company C’s Chief Executive Officer. Although Mr. Franklin engaged in discussion with Company C’s Chief Executive Officer after executing the non-disclosure agreement, Company C indicated that the timing was not right for Company C to engage in a potential business combination with Stellar.

On October 30, 2025, the Stellar Board met informally to receive an update from Stellar’s management and KBW on the reaction of the nine parties that were contacted about a potential business combination with Stellar. In addition, representatives of a publicly traded regional bank holding company that had been contacted by KBW (“Company D”) attended a portion of the Stellar Board meeting to provide a presentation describing a potential business combination transaction between Stellar and Company D.

On November 6, 2025, the Stellar Board held a special meeting which was attended by Justin Long, Stellar’s General Counsel, as well as representatives of KBW to discuss the ongoing outreach by KBW on behalf of Stellar to financial institutions that could be suitable potential business partners for a potential combination transaction involving Stellar. Representatives of KBW reviewed general market and regulatory conditions and recently announced financial institution mergers and also discussed potential acquirers of Stellar. The Stellar Board discussed Stellar’s business plan, competitive position and stock performance and considered the prospects of Stellar’s continued independence and profitable growth under current economic and competitive conditions and the increasing costs to banks of Stellar Bank’s size relative to larger financial institutions. The Stellar Board also discussed potential acquirers already contacted as well as others to be contacted as part of the process. The Stellar Board also discussed with Mr. Long the directors’ fiduciary duties.

On November 10, 2025, Mr. Franklin met with the Chief Executive Officer of a publicly traded large bank holding company (“Company E”) to discuss overall market conditions and to generally gauge Company E’s potential interest in a business combination transaction. Company E indicated it was not presently pursuing acquisitions.

On November 12, 2025, in accordance with Stellar’s directives, KBW contacted Prosperity to schedule a meeting with Mr. Franklin and senior management of Prosperity.

On November 15, 2025, Company D executed a non-disclosure agreement with Stellar to permit further discussions about a potential business combination.

On November 18, 2025, Mr. Franklin and representatives of KBW met with the Chief Executive Officer and executive management of Company D regarding a potential business combination transaction between Stellar and Company D.

On November 19, 2025, Stellar executed a non-disclosure agreement with Prosperity. Also, on November 19, 2025, Mr. Franklin met with David Zalman, Prosperity’s Senior Chairman of the Board and Chief Executive Officer to discuss a potential acquisition of Stellar. From time to time, senior executives of Stellar have had informal conversations with senior executives of other financial institutions regarding industry developments and economic and market conditions, and, prior to the execution of the non-disclosure agreement, Mr. Franklin and Mr. Zalman had previously met on multiple occasions and discussed their respective companies and the prospects for financial institutions in the markets they served.

On November 20, 2025, the Stellar Board met in executive session for an update from Mr. Franklin, Mr. Long, and representatives of KBW on the status of meetings with potential acquirers and the composition of Stellar’s potential acquirer list. The Stellar Board engaged in discussion about Stellar’s business plan and outlook, as well as management succession matters. The Stellar Board, in consultation with the KBW representatives, discussed a process for obtaining indications of interest from interested parties.

 

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On November 24, 2025, Mr. Franklin met with the Chief Executive Officer of Company B to discuss Company B’s vision for a combination with Stellar. Also on November 24, 2025, Mr. Franklin met with the Chief Executive Officer and the Chief Financial Officer of Company E to discuss Company E’s vision for a combination with Stellar.

On November 28, 2025, Company B submitted its non-binding indication of interest to Stellar regarding a potential business combination transaction. Company B proposed an all-stock transaction. In addition, Company B proposed to appoint two Stellar designees to Company B’s board of directors upon the closing of a transaction.

On December 1, 2025, Company D submitted its non-binding indication of interest to Stellar regarding a potential business combination transaction. Company D proposed an all-stock transaction. In addition, Company D proposed to appoint three Stellar designees to Company D’s board of directors upon the closing of a transaction.

On December 5, 2025, which was the deadline communicated by KBW on behalf of Stellar to interested parties to submit bids, Prosperity submitted a non-binding indication of interest to Stellar. Prosperity proposed an acquisition of Stellar for consideration comprised of 70% Prosperity common stock and 30% cash. Prosperity also proposed to appoint one Stellar designee to Prosperity’s board of directors and two Stellar designees to Prosperity Bank’s board of directors upon the closing of a transaction.

No indications of interest from any other parties were received.

On December 9, 2025, at a meeting of the Stellar Board, the Stellar Board held discussions with members of management and representatives of KBW regarding the non-binding indications of interest received from Company B, Company D, and Prosperity. Mr. Franklin reviewed Stellar’s recent stock price, including its price on December 5, 2025 of $31.66, and market multiples and the potential impact on pricing that Stellar’s stock price and multiples would have for the interested parties. The Stellar Board also discussed Stellar’s current operations and outlook, and the regulatory environment’s potential risk to completing a transaction relative to the historical regulatory environment. Representatives of KBW reviewed with the Stellar Board each proposal including financial and business information for each of the interested parties as well as implied transaction valuation metrics, pro forma ownership, board representation, management structure, and timing considerations with respect to each proposed transaction. Based on each of the potential acquirer’s stock prices as of December 5, 2025, Company B’s non-binding proposal implied a per share value for Stellar common stock between $33.98 and $34.64, Company’s D’s non-binding proposal implied a per share value for Stellar common stock between $33.64 and $35.51, and Prosperity’s non-binding proposal implied a per share value for Stellar common stock of $37.95. Representatives of KBW also discussed with the Stellar Board that Prosperity’s non-binding proposal contemplated a 70% stock and 30% cash consideration mix compared to the all-stock proposals from Company B and Company D. The Stellar Board engaged in discussion with representatives of KBW about each of the proposals and the historical price performance and publicly available analyst price targets for the stock of each of the interested parties. The Board also discussed with representatives of KBW the consideration mix and considered that the cash portion of the merger consideration proposed by Prosperity would hedge a portion of the downside risk of the merger consideration between the signing of the merger agreement and closing while it limited the upside associated with an increase in the value of Prosperity’s stock during the pendency of the transaction. The Stellar Board also discussed the comparative strengths and weaknesses of each interested party and the potential synergies that could be achieved by a combination with each such party, among other matters. The Stellar Board further discussed the perceived risks and challenges associated with pursuing a transaction with each party. After evaluating each proposal, the Stellar Board requested that KBW confirm the terms of Prosperity’s proposal and inquire whether Prosperity would agree to appoint an additional Stellar designee to the Prosperity Board upon the closing of a transaction. Following the discussion, the Stellar Board approved continuing discussions exclusively with Prosperity.

Also on December 9, 2025, KBW contacted Prosperity to confirm the financial terms of its proposal and inquire whether Prosperity would agree to appoint a second Stellar designee to the Prosperity Board upon the closing of a transaction.

 

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On December 10, 2025, Prosperity submitted a revised non-binding indication of interest to Stellar contemplating that Prosperity would appoint two Stellar designees to the Prosperity Board and two Stellar designees to the Prosperity Bank board of directors upon the closing of a transaction. The revised non-binding indication of interest also clarified that the merger consideration would consist of approximately 19.4 million shares of Prosperity common stock in the aggregate that would be used to determine the exchange ratio and an aggregate cash amount that would be used to determine the per share cash consideration. Additionally, Mr. Franklin and Mr. Long met with Ms. Charlotte Rasche, the General Counsel of Prosperity to discuss next steps and timing for the process.

On December 10, 2025 and December 11, 2025, Mr. Franklin contacted Company B and Company D, respectively, to advise them that Stellar would not be proceeding with their proposals.

On December 11, 2025, Stellar and Prosperity entered into an exclusivity agreement providing that, until January 28, 2026, Stellar would negotiate exclusively with Prosperity with respect to a business combination involving Stellar. Later the same day, Ramon Vitulli, III, Stellar’s President and Stellar Bank’s Chief Executive Officer, and Paul Egge, Stellar’s Chief Financial Officer, held a call with representatives of Prosperity to discuss the logistics of due diligence.

On December 12, 2025, Prosperity submitted a due diligence request list to Stellar. On December 16, 2025, Stellar submitted a reverse due diligence request list to Prosperity. From December 12, 2025 through January 27, 2026, Stellar and Prosperity conducted due diligence on one another with respect to financial, compliance, risk, operational, legal and other matters.

On December 14, 2025, the Stellar Board approved the formation of a committee of the Stellar Board (the “Stellar Committee”) composed solely of independent and disinterested directors to provide oversight of merger negotiations with Prosperity, to regularly confer with and advise management regarding the terms of the transaction, and to report to the Stellar Board regarding the status of negotiations with Prosperity. The Stellar Committee consisted of John Beckworth, Reagan A. Reaud, Joseph B. Swinbank, and John Eddie Williams.

On December 16, 2025, Mr. Vitulli met with Mr. Zalman and Ms. Rasche to discuss Prosperity’s plans for employment agreements and retention agreements with certain Stellar employees, but did not discuss any compensation terms of any Stellar employees.

On December 20, 2025, the Stellar Committee met with representatives of Stellar management and representatives of KBW. Representatives of KBW provided an update with respect to discussions with representatives of Prosperity since the Stellar Board met on December 9, 2025. Mr. Franklin reviewed the conversations with Prosperity regarding the expectations and treatment of Stellar employees in the proposed transaction. He noted that Prosperity typically conditioned merger announcements on target employees, usually lending staff, entering into employment agreements. The Stellar Committee also discussed the requirements of Stellar’s change in control severance plan and plans for retention of employees during the pendency of the transaction. The Stellar Committee then discussed the performance of Prosperity’s stock and the impact of the part-cash/part-stock merger consideration. Finally, the Stellar Committee inquired as to Mr. Franklin’s proposed role with Prosperity following the consummation of the acquisition. Mr. Franklin reviewed his discussions with Mr. Zalman on that topic, which had been general in nature with no discussion regarding the terms or compensation. Mr. Long concluded the meeting by reminding the Stellar Committee members of their fiduciary duties and the process by which the Stellar Board would ultimately be asked to approve the merger and the merger agreement.

On December 22, 2025, Mr. Franklin and Mr. Vitulli met with Mr. Zalman and Ms. Rasche to discuss various terms of the proposed merger.

On December 23, 2025, the Stellar Committee met with members of Stellar management, representatives of KBW, and representatives of Norton Rose Fulbright US LLP (“Norton Rose”), Stellar’s legal counsel, to discuss

 

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the status of negotiations with Prosperity. The Stellar Committee reviewed its prior discussions regarding the Prosperity proposal, including the merger consideration mix, Prosperity’s historical stock performance and the potential for volatility in Prosperity’s stock price between announcement of a transaction and its closing. Mr. Franklin updated the Stellar Committee on his discussions with Prosperity regarding its plans to offer post-closing employment to certain key employees pre-announcement of the transaction and Prosperity’s post-closing employee retention and compensation plans for current Stellar Bank employees. Lastly, the Stellar Committee discussed the timing of execution of a definitive agreement and the regulatory approval process.

On December 29, 2025, Mr. Vitulli met with representatives of Prosperity to discuss retention planning for Stellar employees and the proposed organizational chart of the combined company.

On December 30, 2025, the Stellar Committee met with members of Stellar management, and representatives of KBW and Norton Rose. Mr. Franklin advised the Stellar Committee on the progress related to Prosperity’s proposed post-closing employment terms for certain key employees and Prosperity’s post-closing employee retention and compensation plans for current Stellar Bank employees and the status of due diligence. The KBW representatives reviewed the terms and structures of similar precedent transactions and compared Prosperity’s historical stock performance to relevant indices.

On January 2, 2026, Mr. Vitulli met with representatives of Prosperity to continue discussions regarding employment and retention of Stellar employees in connection with the merger.

On January 6, 2026, the Stellar Committee met with members of management and representatives of KBW and Norton Rose. Mr. Franklin updated the Stellar Committee on the status of due diligence and Prosperity’s expectations regarding employment agreements with Stellar’s lending staff and retention agreements with other Stellar employees.

Also on January 6, 2026, Wachtell, Lipton, Rosen & Katz, Prosperity’s legal counsel (“Wachtell Lipton”), had a call with Norton Rose to discuss a draft merger agreement and proposed timing and terms of the proposed transaction. Later that day, Wachtell Lipton circulated the first draft of the merger agreement to Norton Rose.

Between January 6, 2026 and January 13, 2026, Stellar, with the assistance of Norton Rose and KBW, reviewed the merger agreement and discussed various business and legal issues contained in the merger agreement.

On January 13, 2026, the Stellar Committee met with management of Stellar and representatives of KBW and Norton Rose. Mr. Franklin updated the Stellar Committee regarding the status of due diligence and negotiations with Prosperity, including the post-closing employee retention and compensation plans for current Stellar Bank employees. The Stellar Committee discussed the proposed timing of an announcement of the transaction. Representatives of Norton Rose described the draft of the merger agreement provided by Wachtell Lipton and that it was generally consistent with Prosperity’s revised indication of interest dated December 10, 2025. Later on January 13, 2026, Norton Rose delivered a revised draft of the merger agreement to Wachtell Lipton.

On January 14, 2026, Mr. Franklin, Mr. Vitulli, and Mr. Long met with Mr. Zalman and other Prosperity executives to discuss retention agreements for Stellar employees who would not be asked to sign employment agreements.

Also on January 14, 2026, Wachtell Lipton delivered a draft of the voting agreement to Norton Rose.

On January 16, 2026, Mr. Vitulli met again with Prosperity executives to negotiate retention plans. Stellar also conducted a reverse due diligence call with Prosperity executives, including Mr. Zalman.

Also on January 16, 2026, Wachtell Lipton delivered to Norton Rose a revised draft of the merger agreement. From January 16, 2026 until January 27, 2026, Norton Rose and Wachtell Lipton continued to negotiate the terms of the merger agreement and other ancillary documents. Wachtell Lipton’s January 6 draft of

 

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