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Exhibit 5.1
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Seaport West
155 Seaport Boulevard
Boston, MA 02210-2600

617 832 1000 main
617 832 7000 fax




October 31, 2025


Butterfly Network, Inc.
1600 District Avenue
Burlington, MA 01803

Re:    Registration Statement on Form S-8

To the Addressees:
We are familiar with the Registration Statement on Form S-8 (the “Registration Statement”) being filed by Butterfly Network, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), on the date hereof. The Registration Statement relates to the offer and sale by the Company of up to 10,651,753 shares (the “Shares”) of its Class A common stock, par value $0.0001 per share (the “Common Stock”), consisting of (a) 8,575,266 shares of Common Stock (the “2020 Plan Shares”) issuable under the Company’s Amended and Restated 2020 Equity Incentive Plan (the “2020 Plan”) and (b) 2,076,487 shares of Common Stock (the “2024 ESPP Shares”) issuable under the Company’s 2024 Employee Stock Purchase Plan (the “2024 ESPP”).
In arriving at the opinion expressed below, we have examined the Company’s Third Amended and Restated Certificate of Incorporation and the Company’s Amended and Restated Bylaws, the records of meetings and consents of the Company’s Board of Directors, or committees thereof, records of the proceedings of its stockholders deemed to be relevant to this opinion letter, the 2020 Plan and the 2024 ESPP, each as provided to us by the Company, and the Registration Statement.
In addition, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. In our examination, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to authentic original documents of all documents submitted to us as copies and the due authorization, execution and delivery of all documents by all persons other than the Company, where authorization, execution and delivery are prerequisites to the effectiveness of such documents. We have also made such investigations of law as we have deemed appropriate as a basis for the opinion expressed below.
We have assumed that the purchase price or other consideration to be received by the Company for the Shares will be valid consideration equal to or in excess of the par value thereof.
In rendering the opinion expressed below, we express no opinion other than as to the Delaware General Corporation Law.
On the basis of the foregoing, it is our opinion that (i) the 2020 Plan Shares, when issued and delivered in accordance with the terms of the 2020 Plan and the awards thereunder and (ii) the 2024 ESPP Shares, when issued and delivered in accordance with the terms of the 2024 ESPP, in each case against the Company’s receipt of the purchase price or other consideration therefor, will be validly issued, fully paid and non-assessable.




This opinion is to be used only in connection with the offer and sale of the Shares while the Registration Statement is in effect.
This opinion is being delivered solely for the benefit of the Company and such other persons as are entitled to rely upon it pursuant to the applicable provisions of the Securities Act. This opinion may not be used, quoted, relied upon or referred to for any other purpose, nor may it be used, quoted, relied upon or referred to by any other person, for any purpose, without our prior written consent.
This opinion is based upon currently existing statutes, rules and regulations and judicial decisions and is rendered as of the date hereof, and we disclaim any obligation to advise you of any change in any of the foregoing sources of law or subsequent developments in law or changes in facts or circumstances which might affect any matters or opinions set forth herein.
We consent to the filing of this opinion as an exhibit to the Registration Statement. In giving such consent, we do not admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.
This opinion letter shall be interpreted in accordance with the Core Opinion Principles jointly issued by the Committee on Legal Opinions of the American Bar Association’s Business Law Section and the Working Group on Legal Opinions Foundation as published in 74 Business Lawyer 815 (2019).    
                        Very truly yours,


FOLEY HOAG LLP
By:
/s/ Stacie S. Aarestad
a Partner