Company: ARMP
Filing Date: 2025-08-13
Form Type: S-3
Source: 0001104659-25-077648
Chunk: 0

Company: Armata Pharmaceuticals, Inc.
Filing Date: 2025-08-13
Form: S-3
Chunk 0
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<div align='center'>As filed with the Securities and Exchange Commission on August 13, 2025</div>

Registration No. 333-

<div align='center'>UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form S-3

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Armata Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)</div>

| Washington                        | 91-1549568             |
| (State or other jurisdiction      | (I.R.S. Employer       |
| of incorporation or organization) | Identification Number) |

<div align='center'>5005 McConnell Avenue

Los Angeles, California 90066

(310) 665-2928

(Address, including zip code, and telephone number,
including area code, of registrant’s principal executive offices)

Deborah L. Birx, M.D.

Chief Executive Officer

Armata Pharmaceuticals, Inc.

5005 McConnell Avenue

Los Angeles, California 90066

(310) 665-2928

(Name, address, including zip code, and telephone number,

including area code, of agent for service)

Copies to:

Jared N. Fertman

Andrew C. Marmer

Willkie Farr & Gallagher LLP

787 Seventh Avenue

New York, New York 10019

(212) 728-8000</div>

(Approximate date of commencement of proposed sale to the public) From time to time after the effective date of this Registration Statement, as determined by the registrant.

If the only securities being registered on this Form are being offered pursuant to dividend or interest reinvestment plans, please check the following box:¨

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box:x

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.¨