USA Rare Earth Inc美股招股说明书(2026-01-29版)

USA Rare Earth, Inc. Thisprospectus supplement updates,amends and supplements the prospectus dated October 27,2025(the“Prospectus”), which forms a part of our Registration Statement on Form S-1 (Registration No. 333-290723). Capitalizedtermsused in this prospectus supplement and not otherwise defined herein have the meanings specified in theProspectus. This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectuswith the information contained in: •our Current Report on Form 8-K filed with the SEC on January29, 2026, excluding Item 7.01 and Exhibit 99.1,which is set forth below. This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read inconjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by referencethereto, except to the extent that the information in this prospectus supplement updates or supersedes the informationcontained in the Prospectus. Please keep this prospectus 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”. On January28, 2026, the closing price of our Common Stock was $25.18 per share. We are an “emerging growth company” and a “smaller reporting company” as such terms are defined under the federalsecurities laws and, 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 uncertaintiesdescribed under the heading “Risk Factors” of the Prospectus, and under similar headings in any amendmentsor supplements to the Prospectus. Neither the SEC nor any state securities commission has approved or disapproved of these securities ordetermined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to thecontrary is a criminal offense. The date of this prospectus supplement is January29, 2026. 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): January28, 2026 USA Rare Earth, Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 98-1720278 (State or Other Jurisdiction ofIncorporation) (I.R.S. Employer Identification No.) 100 W. Airport Road, Stillwater, OK 74075(Address of Principal Executive Offices) (Zip Code) (813) 867-6155(Registrant’s telephone number, including area code) Not applicable(Former Name or Former Address, if Changed Since Last Report) Check the appropriate box below if the Form8-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 Rule12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company☑ 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.☐ Item 1.01 - Entry into a Material Definitive Agreement Private Placement As previously announced in our Current Report on Form 8-K, dated January 26, 2026, on January 26, 2026, USA RareEarth, Inc., a Delaware corporation (the “Company”), entered into a securities purchase agreement (the “PurchaseAgreement”) with the several purchasers named therein (the “Purchasers”), for the private placement (the “PrivatePlacement”) of 69,767,442 shares of the Company’s common stock, par value $0.0001 per share (the “Shares”), foraggregate gross proceeds of approximately $1.5 billion, at a price per share of $21.50. On January 28, 2026 (the “ClosingDate”), the Company closed the Private Placement and issued the Shares (the “Closing”). The Company intends to usethe net proceeds from the Private Placement to accelerate the build-out of its mine-to-magnet value chain, including thedevelopment and expansion of mining, processing, metal-making and magnet manufacturing capabilities, as well as forworking capital and general corporate purposes. The Private Placement is exempt from the registration requirements of the Securities Act pursu