UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-A

FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES

PURSUANT TO SECTION 12(b) OR (g) OF THE

SECURITIES EXCHANGE ACT OF 1934

Castellum, Inc.

(Exact name of registrant as specified in its charter)

Securities to be registered pursuant to Section 12(b) of the Act:

If this form relates to the registration of a class of securities pursuant to Section 12(b) of the Exchange Act and is effective pursuant to General Instruction A.(c) or (e), check the following box. x

If this form relates to the registration of a class of securities pursuant to Section 12(g) of the Exchange Act and is effective pursuant to General Instruction A.(d) or (e), check the following box. ¨

If this form relates to the registration of a class of securities concurrently with a Regulation A offering, check the following box. ¨

Securities Act registration statement or Regulation A offering statement file number to which this form relates:

333-267249

Securities to be registered pursuant to Section 12(g) of the Act:

None

INFORMATION REQUIRED IN REGISTRATION STATEMENT

Item 1. Description of Registrant’s Securities to be Registered.

The securities to be registered hereby are the common stock, $0.0001 par value per share (the “Common Stock”), of Castellum, Inc. (the “Company”). The description of the Common Stock set forth under the heading “Description of Securities” and under the further heading “Common Stock”, contained in the Company’s Registration Statement on Form S-1 (File No. 333-267249) (the “Registration Statement”), initially filed with the Securities and Exchange Commission on September 2, 2022, as subsequently amended by any amendments to such Registration Statement and by any form of prospectus filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended, in connection with such Registration Statement, is incorporated herein by reference. The Common Stock is expected to be listed on the NYSE American LLC.

Item 2. Exhibits.

Pursuant to the instructions as to exhibits with respect to Form 8-A, no exhibits are required to be filed because no other securities of the Company are registered on the NYSE American LLC and the securities registered hereby are not being registered pursuant to Section 12(g) of the Securities Exchange Act of 1934, as amended.

SIGNATURES

Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereto duly authorized.