USA Rare Earth Inc美股招股说明书(2025-09-29版)

PROSPECTUS SUPPLEMENT No. 3(to Prospectus dated July 2, 2025) USA RARE EARTH, INC. This prospectus supplement updates, amends and supplements the prospectus dated July 2, 2025 (the “Prospectus”), which forms apart of our Registration Statement on Form S-1 (Registration No. 333-287411). Capitalized terms used in this prospectus supplementand not otherwise defined herein have the meanings specified in the Prospectus. This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectus with theinformation contained in: ●our Current Report on Form 8-K filed with the SEC on September 29, 2025, excluding Item 7.01 and Exhibits 99.1 and 99.2,which is set forth below. This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction withthe Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent thatthe information in this prospectus supplement updates or supersedes the information contained in the Prospectus. Please keep thisprospectus supplement with your Prospectus for future reference. USA Rare Earth, Inc.’s Common Stock and Warrants are listed on the Nasdaq Stock Market LLC under the symbols “USAR” and“USARW,” respectively. On September 26, 2025, the closing price of our Common Stock was $17.33 per share and the closing priceof our Warrants was $7.1932 per Warrant. We are an “emerging growth company” and a “smaller reporting company” as such terms are defined under the federal securities lawsand, as such, are subject to certain reduced public company reporting requirements. Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties describedunder the heading “Risk Factors” of the Prospectus, and under similar headings in any amendments or supplements to theProspectus. Neither the SEC nor any state securities commission has approved or disapproved of these securities or determined if theProspectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense. The date of this prospectus supplement is September 29, 2025. UNITED STATESSECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d)OF THE SECURITIES EXCHANGE ACT OF 1934 Date of Report (Date of earliest event reported): September 24, 2025 USA Rare Earth, Inc.(Exact name of registrant as specified in its charter) 98-1720278 (IRS. EmployerIdentification No.) Registrant’s telephone number, including area code:(813) 867-6155 N.A.(Former name or former address, if changed since last report) Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrantunder any of the following provisions: Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) Securities registered pursuant to Section 12(b) of the Act: Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933(§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period forcomplying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ Private Placement Securities Purchase Agreement; Registration Rights Agreement On September 24, 2025 (the “Signing Date”), USA Rare Earth, Inc., a Delaware corporation (the “Company”) entered into asecurities purchase agreement (the “Purchase Agreement”) with the purchaser named therein (the “Purchaser”), for the privateplacement (the “Private Placement”) of 8,333,333 shares of the Company’s common stock, par value $0.0001 per share (the“Securities”) for aggregate gross proceeds of $125,000,000. On September 29, 2025, the Company closed the Private Placement andissued the Securities. The Company intends to use the net proceeds from the Private Placement for general corporate purposes. The Purchase Agreement also contains customary representations, warranties, covenants and agreements by the Company,indemnification obligations of the Company and the Purchaser, including for liabilities under the Securities Act of 1933, as amended(the “Securities Act”), and other obligations of the parties. The representations, warranties, covenants and agreements contained in thePurchase Agreement reflect negotiations between the parties to the Purchase