NioCorp Developments Ltd美股招股说明书(2025-10-14版)

We are offering 10,152,175 of our common shares, without par value (“Common Shares”), and, in lieu of Common Shares tocertain investors that so choose, 5,925,000 pre-funded Warrants (as defined herein) to purchase an aggregate of 5,925,000 CommonShares (the “Pre-Funded Warrants”). The purchase price of each Pre-Funded Warrant will equal the price per share at which eachCommon Share is sold in this offering, minus $0.0001, which is the exercise price of each Pre-Funded Warrant. The Pre-FundedWarrants will not have an expiration date and will be immediately exercisable. The offering price for each Common Share is $9.34.This prospectus supplement also relates to the offering of Common Shares issuable upon exercise of the Pre-Funded Warrants. TheCommon Shares and Pre-Funded Warrants are being sold on a “reasonable best efforts” basis. See “Plan of Distribution.” Our Common Shares trade on the Nasdaq Global Market under the symbol “NB.” On October 10, 2025, the last reported saleprice of our Common Shares on the Nasdaq Global Market was $10.39 per Common Share. There is no established trading market forthe Pre-Funded Warrants and we do not expect a market to develop. In addition, we do not intend to list the Pre-Funded Warrants onany national securities exchange or any other nationally recognized trading system. Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page S-6 of this prospectussupplement and on page 2 of the accompanying prospectus, and the documents incorporated by reference herein and therein. Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved ordisapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful orcomplete. Any representation to the contrary is a criminal offense. We have engaged Maxim Group LLC (the “Placement Agent”) to act as our exclusive placement agent in connection with thisoffering. The Placement Agent has agreed to use its reasonable best efforts to solicit offers for the securities offered by this prospectussupplement and accompanying prospectus. The Placement Agent does not have any obligation to sell any specific number or dollaramount of the securities being offered hereby, nor are we requiring any minimum purchase or sale of any specific number of securitiesin order for us to consummate this offering and there are no arrangements to place the funds in an escrow, trust, or similar account. ThePlacement Agent is not purchasing or selling any of the securities we are offering. We have agreed to pay the Placement Agent thecommissions set forth in the table below. See “Plan of Distribution” beginning on page S-28 of this prospectus supplement for moreinformation regarding these arrangements. (1)We have agreed to pay the Placement Agent a cash placement commission equal to 7.00% of the aggregate proceeds from thesale of the Common Shares and the Pre-Funded Warrants sold in this offering to the investors. The Company has agreed toreimburse the Placement Agent for certain expenses incurred in connection with this offering. See “Plan of Distribution” foradditional disclosure regarding the Placement Agent’s compensation. The securities are expected to be delivered on or about October 15, 2025, subject to satisfaction of customary closingconditions. Sole Placement Agent Maxim Group LLC The date of this prospectus supplement is October 13, 2025. TABLE OF CONTENTS Prospectus Supplement About This Prospectus SupplementWhere You Can Find More InformationIncorporation of Documents by ReferenceProspectus Supplement SummaryRisk FactorsCautionary Note Regarding Forward-Looking StatementsUse of ProceedsDilutionDescription of SecuritiesCertain United States Federal Income Tax ConsiderationsCertain Canadian Federal Income Tax Considerations for U.S. ResidentsPlan of DistributionLegal MattersExperts Prospectus About This ProspectusWhere You Can Find More InformationInformation Incorporated by ReferenceSummaryRisk FactorsCautionary Note Regarding Forward-Looking StatementsUse of ProceedsDescription of Capital StockDescription of WarrantsDescription of Debt SecuritiesDescription of UnitsPlan of DistributionLegal MattersExperts ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement and the accompanying prospectus are part of a registration statement on Form S-3 that we filedwith the SEC on October 10, 2025 using a “shelf” registration process. This prospectus supplement describes the specific terms of the securities we are offering and adds to, and updates,information in the accompanying prospectus and the documents incorporated by reference herein and therein. If there is a conflictbetween the information contained in this prospectus supplement and the information contained in the accompanying prospectus orany document incorporated by reference into it or into this prospectus supplement that was filed with the SEC before the