Eos Energy Enterprises Inc. (EOSE) filed a Form 8K - Other Events - with the U.S Securities and Exchange Commission on July 02, 2026.

Rights Offering

On July 2, 2026, Eos Energy Enterprises, Inc. (the "Company") issued a press release announcing the commencement of its previously-announced rights offering pursuant to a shelf registration statement filed on Form S-3 (File No. 333-295819) (the "Registration Statement") with the Securities and Exchange Commission ("SEC") on May 13, 2026, and the prospectus supplement relating to the rights offering filed with the SEC on July 2, 2026 (the prospectus supplement together with the accompanying prospectus, the "Prospectus").

In connection with the rights offering, the Company is filing certain ancillary documents as Exhibits 4.1, 4.2, 4.3, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, and 99.7 to this Current Report on Form 8-K for the purpose of incorporating such items by reference to the Registration Statement, of which the Prospectus forms a part. The Company is also filing as Exhibit 5.1 the opinion of Davis Polk & Wardwell LLP in connection with the issuance of the subscription rights and the Company's common stock, par value $0.0001 per share ("Common Stock"), and warrants to purchase shares of Common Stock, issuable upon exercise of such subscription rights.

This Current Report on Form 8-K does not constitute an offer to sell or the solicitation of an offer to buy the securities described herein, nor will there be any sale of such securities in any state or other jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction. The rights offering will be made only by means of the Prospectus, which can be accessed through the SEC's website at www.sec.gov. A copy of the Prospectus may also be obtained by contacting the information agent for the rights offering, Sodali & Co., at (203) 658-9400 (banks and brokers), (833) 225-0490 (individuals call toll-free) or EOSE.info@investor.sodali.com.

A copy of the press release related to the matters set forth herein is attached hereto as Exhibit 99.7 and is incorporated herein by reference.

The full text of this SEC filing can be retrieved at: https://www.sec.gov/Archives/edgar/data/1805077/000095010326010023/dp249395_8k.htm

Any exhibits and associated documents for this SEC filing can be retrieved at: https://www.sec.gov/Archives/edgar/data/1805077/000095010326010023/0000950103-26-010023-index.htm

Public companies must file a Form 8-K, or current report, with the SEC generally within four days of any event that could materially affect a company's financial position or the value of its shares.