Exhibit 5.1

November 4, 2025

Babcock & Wilcox Enterprises, Inc.

1200 East Market Street, Suite 650

Akron, OH 44305

We have acted as special counsel to Babcock & Wilcox Enterprises, Inc., a Delaware corporation (the “Company”), in connection with the sale from time to time by the Company of its common stock, par value $0.01 per share (the “Common Stock”), having an aggregate offering price of up to $200,000,000 (the “Shares”), pursuant to the Sales Agreement, dated as of November 4, 2025 (the “Sales Agreement”). The Common Stock is being offered and sold pursuant to the registration statement on Form S-3 (File No. 333-283368) (the “Registration Statement”), filed by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”) on November 21, 2024 and declared effective by the Commission on April 8, 2025.

In our capacity as such counsel, we have examined originals or copies of those corporate and other records and documents we considered appropriate, including, among other things, the following:

We have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals and the conformity with originals of all documents submitted to us as copies.

Century City • Los Angeles • Newport Beach • New York • San Francisco • Silicon Valley • Washington, DC

Beijing • Brussels • Hong Kong • London • Seoul • Shanghai • Singapore • Tokyo

Based on this examination, our reliance upon the assumptions in this letter and our consideration of those questions of law we considered relevant, and subject to the limitations and qualifications in this letter, we are of the opinion that:

The issuance and sale of the Shares has been duly authorized by all necessary corporate action on the part of the Company, and upon payment for and delivery of the Shares in accordance with the Agreement, the Shares will be validly issued, fully paid and non-assessable.

The law covered by this letter is limited to the present General Corporation Law of the State of Delaware. We express no opinion as to the laws of any other jurisdiction and no opinion regarding the statutes, administrative decisions, rules, regulations or requirements of any county, municipality, subdivision or local authority of any jurisdiction.

This letter is being furnished in accordance with the requirements of Item 601(b)(5) of Regulation S-K promulgated under the Securities Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement, the prospectus included in the Registration Statement or any prospectus supplement, other than as expressly stated herein with respect to the Shares. This letter is expressly limited to the matters set forth above, and we render no opinion, whether by implication or otherwise, as to any other matters. This letter speaks only as of the date hereof and we assume no obligation to update or supplement this letter to reflect any facts or circumstances that arise after the date hereof and come to our attention, or any future changes in laws.

We hereby consent to the incorporation by reference of this letter as Exhibit 5.1 to the Registration Statement and to the reference to this firm under the heading “Legal Matters” in the Registration Statement and related prospectus. In giving such consent, we do not hereby admit that we are within the category of persons whose consent is required under Section 7 of the Securities Act or the rules or regulations of the Commission thereunder.

Respectfully submitted,

/s/ O’Melveny & Myers LLP