Material Event (Form 8-K)

Momentus Inc. (the "Company"), is a party to 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 $75 million 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"). This aggregate principal amount does not include shares of the Company's common stock sold pursuant to the Sales Agreement before today's date.

Any additional 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- 296218) initially filed with the Securities and Exchange Commission (the "SEC") on May 26, 2026 (the "Registration Statement") and declared effective by the SEC on June 4, 2026, and the prospectus supplement relating to the ATM Offering filed with the SEC on June 18, 2026.

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.