T3 Defense Inc.

As filed with the Securities and Exchange Commission on September 3, 2026.

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMS-1

REGISTRATION STATEMENT

UNDER THE SECURITIES ACT OF 1933

T3 Defense Inc.

(Exact name of registrant as specified in its charter)

575 Fifth Ave., 14th Floor

New York, New York 10017

(646) 257-4214

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

Menachem Shalom

T3 Defense Inc.

Chief Executive Officer

575 Fifth Ave., 14th Floor

New York, New York 10017

(646) 257-4214

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Robert Cohen

McDermott Will & Schulte LLP

333 SE 2nd Avenue, Suite 4500

Miami, Florida 33131

(561) 287-7096

Approximate date of commencement of proposed sale to the public:

As soon as practicable after the effective date hereof.

If any 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, check the following box. ☒

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. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) 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. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act.☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with section 8(a) of the Securities Act of 1933 or until the registration statement shall become effective on such date as the Securities and Exchange Commission acting pursuant to said section 8(a), may determine.

The information in this prospectus is not complete and may be changed. The selling stockholders may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state or jurisdiction where the offer or sale is not permitted.

PRELIMINARY PROSPECTUS

SUBJECT TO COMPLETION, DATED SEPTEMBER 3, 2026

T3 Defense Inc.

5,100,000 Shares of Common Stock

This prospectus relates to the resale from time to time by the selling stockholders named in this prospectus, including their transferees, pledgees, donees or successors (the “Selling Stockholders”), of up to 5,100,000 shares (the “Shares”) of the common stock, par value $0.0001 per share (the “Common Stock”), of T3 Defense Inc., a Delaware corporation (the “Company” or “T3”), which consists of (i) up to 1,100,000 Shares (the “Conversion Shares”) issuable upon the conversion of shares of our Series B Convertible Preferred Stock, par value $0.0001 per share (the “Series B Preferred Stock”) (or pre-funded warrants in lieu thereof (the “Pre-Funded Warrants”)), and (ii) up to 4,000,000 Shares (the “Warrant Shares”) issued or issuable upon the exercise of common warrants (the “Common Warrants”). The shares of Series B Preferred Stock and the Common Warrants were purchased or are to be purchased by the Selling Stockholders in a private placement (the “February 2026 Private Placement”) pursuant to the Securities Purchase Agreement, dated February 24, 2026, by and between the Company and a certain accredited investor (the “Securities Purchase Agreement”). In connection with the February 2026 Private Placement, we entered into a Registration Rights Agreement, dated February 24, 2026 (the “Registration Rights Agreement”), with such accredited investor. We previously registered the resale of 30,000,000 shares of Common Stock (on a pre-Reverse Stock Split (as defined below) basis) pursuant to a registration statement on Form S-1 (File No. 333-296513) declared effective by the Securities and Exchange Commission on June 30, 2026 (the “Prior Registration Statement”). This registration statement is being filed to register additional shares as required by Section 3.3 of the Registration Rights Agreement.

Each share of Series B Preferred Stock has a stated value of $50,000 (the “Stated Value”). Each share of Series B Preferred Stock issued in the first tranche of the February 2026 Private Placement is currently convertible into 2,339 Conversion Shares (or Pre-Funded Warrants in lieu thereof), calculated by dividing the Stated Value by the current conversion price equal to $21.375 per share of Series B Preferred Stock (the “Conversion Price”). The Conversion Price was initially $2.13 per share (on a pre-Reverse Stock Split basis), was subsequently adjusted to $0.171 per share (on a pre-Reverse Stock Split basis) by reference to the market price of our Common Stock on June 30, 2026, the date on which the Prior Registration Statement was declared effective, and was adjusted again to $21.375 after giving effect to the Reverse Stock Split. Each share of Series B Preferred Stock to be issued in the second tranche of the February 2026 Private Placement will have a Conversion Price equal to the trading price of the Common Stock on the day this registration statement is declared effective. The Conversion Price is subject to further adjustment upon stock splits, distributions, reorganizations, reclassifications, change of control and the like, and is also subject to price-based anti-dilution adjustments for subsequent offerings made by the Company while the Series B Preferred Stock remains outstanding (subject to certain exempt issuances). The shares of Series B Preferred Stock are subject to a blocker provision (the “Preferred Blocker”), which restricts the conversion of the Series B Preferred Stock if, as a result of such conversion, the holder, together with its affiliates and any other person whose beneficial ownership of Common Stock would be aggregated with the holder’s for purposes of Section 13(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), would beneficially own in excess of 9.9% of our then issued and outstanding shares of Common Stock (including the shares of Common Stock issuable upon such exercise).

Each Common Warrant issued in the first tranche of the February 2026 Private Placement is exercisable for one share of Common Stock at an exercise price of $266.25 per share, subject to adjustment for stock splits, distributions and the like (the “Exercise Price”). The Exercise Price was initially $2.13 per share and was adjusted to $266.25 after giving effect to the Reverse Stock Split. Each Common Warrant to be issued in the second tranche of the February 2026 Private Placement will have an Exercise Price equal to the trading price of the Common Stock on the day this registration statement is declared effective. The Exercise Price is subject to price-based anti-dilution adjustments for subsequent offerings made by the Company while the Common Warrants remain outstanding (subject to certain exempt issuances). The holder of the Common Warrants may exchange the Common Warrants on a cashless basis for a number of shares of Common Stock determined by multiplying the total number of Warrant Shares with respect to which the Common Warrant is then being exercised by the Black Scholes Value (as defined in the Common Warrant) divided by the lower of the two closing bid prices of the Common Stock in the two days prior the time of such exercise, but in any event not less than $1.25 (as may be adjusted for stock dividends, subdivisions, or combinations and the like). The Common Warrants are subject to a blocker provision (the “Warrant Blocker” and, together with the Preferred Blocker, the “Blockers”), which restricts the exercise of a Common Warrant if, as a result of such exercise, the holder, together with its affiliates and any other person whose beneficial ownership of Common Stock would be aggregated with the holder’s for purposes of Section 13(d) of the Exchange Act, would beneficially own in excess of 9.99% of our then issued and outstanding shares of Common Stock (including the shares of Common Stock issuable upon such exercise).

On July 20, 2026, the Company effected a reverse stock split of its issued and outstanding shares of Common Stock at a ratio of 1-for-125 (the “Reverse Stock Split”). Unless noted otherwise, all share and price per share information in this prospectus for all periods presented reflect the Reverse Stock Split.

The Shares being registered for resale represent a considerable percentage of our public float, and the sales of such Shares, or the perception that these sales could occur, could cause the market price of the Common Stock to decline significantly. In addition, we are not selling any shares of Common Stock under this prospectus and will not receive any of the proceeds from the sale of Shares by the Selling Stockholders. We are paying the cost of registering the Shares as well as various related expenses. The Selling Stockholders are responsible for all selling commissions, transfer taxes and other costs related to the offer and sale of its Shares. We will, however, receive the net proceeds of any Common Warrants exercised for cash. For a description of the transaction pursuant to which this resale registration statement relates, please see “Prospectus Summary – February 2026 Private Placement.”

The Selling Stockholders may sell the Shares at fixed prices, at market prices prevailing at the time of sale, at prices related to prevailing market prices or at negotiated prices. The Selling Stockholders may sell the Shares to or through underwriters, broker-dealers or agents, who may receive compensation in the form of discounts, concessions or commissions from the Selling Stockholders, the purchaser of the Shares, or both.

Our Common Stock is presently listed on the Nasdaq Global Market (“Nasdaq”) under the symbol “DFNS.” The closing price for our Common Stock on September 2, 2026, as reported by Nasdaq, was $9.26 per share.

We are an “emerging growth company” as the term is used in the Jumpstart Our Business Startups Act of 2012 and, as such, have elected to comply with certain reduced public company reporting requirements for this prospectus and future filings.

Investing in our securities involves a high degree of risk. You should carefully consider the risks and uncertainties described under the heading “Risk Factors” beginning on page 12 of this prospectus before making a decision to purchase our securities.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

The date of this prospectus is , 2026

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