Material Event (Form 8-K)

As previously reported, on September 19, 2025, Momentus Inc. (the "Company"), entered into a Sales Agreement (the "Sales Agreement") with A.G.P./Alliance Global Partners (the "Agent"), pursuant to which the Company may sell, from time to time, at its option, up to $7,350,000 in aggregate principal amount of an indeterminate amount of shares (the "Shares") of the Company's Class A common stock, par value $0.00001 per share, through the Agent, as the Company's sales agent (the "ATM Offering").

Any Shares to be offered and sold under the Sales Agreement will be issued and sold (i) by methods deemed to be an "at-the-market offering" as defined in Rule 415(a)(4) promulgated under the Securities Act of 1933, as amended, or in negotiated transactions, if authorized by the Company, and (ii) pursuant to the Company's Registration Statement on Form S-3 (File No. 333-290425) filed with the Securities and Exchange Commission (the "SEC") on September 22, 2025 (the "Registration Statement") and declared effective by the SEC on September 30, 2025, and the prospectus supplement relating to the ATM Offering filed with the Registration Statement on September 22, 2025.

This Current Report on Form 8-K shall not constitute an offer to sell or the solicitation of an offer to buy the Shares nor shall there be any sale of the Shares in any state in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state.

The opinion of the Company's legal counsel, Bradley Arant Boult Cummings LLP, regarding the validity of the Shares is filed as Exhibit 5.1 hereto. This opinion is also filed with reference to, and is hereby incorporated by reference into, the Registration Statement.