Fusion Fuel Green PLC-A美股招股说明书(2026-07-29版)

Up to $6,619,798 FUSION FUEL GREEN PLC Class A Ordinary Shares This prospectus supplement relates to an offering and sale of the Class A ordinary shares with a nominal value of $0.0035 each (“ClassA Ordinary Shares”) of Fusion Fuel Green PLC, an Irish public limited company (“we,” “us,” “our,” “Fusion Fuel,” or the“Company”), pursuant to an At The Market Offering Agreement between the Company and H.C. Wainwright & Co., LLC(“Wainwright”), dated May 16, 2025 (the “ATM Agreement”). In accordance with the terms of the ATM Agreement, under thisprospectus supplement and the accompanying prospectus we may offer and sell Class A Ordinary Shares having an aggregate offeringprice of up to $6,619,798 from time to time through Wainwright, acting as sales agent or principal. Sales of our Class A Ordinary Shares, if any, under this prospectus supplement will be made by any method permitted by law that isdeemed an “at the market offering” as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended (the “Securities Act”),including sales made directly on or through The Nasdaq Capital Market, the existing trading market for our Ordinary Shares, salesmade to or through a market maker other than on an exchange or otherwise, directly to Wainwright as principal, in negotiatedtransactions at market prices prevailing at the time of sale or at prices related to such prevailing market prices, and/or in any othermethod permitted by law. Wainwright is not required to sell any specific amount, but will act as our sales agent using commerciallyreasonable efforts consistent with its normal trading and sales practices on mutually agreed terms between Wainwright and us. There isno arrangement for funds to be received in any escrow, trust or similar arrangement. Wainwright will be entitled to compensation at a commission rate equal to 3.0% of the gross sales price of our Class A OrdinaryShares sold through it pursuant to the ATM Agreement. In connection with the sale of the Class A Ordinary Shares on our behalf,Wainwright may be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of Wainwright maybe deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution toWainwright with respect to certain liabilities, including liabilities under the Securities Act. Our Class A Ordinary Shares are listed on The Nasdaq Capital Market tier of The Nasdaq Stock Market LLC (“Nasdaq”) under thesymbol “HTOO”. The last sale price of the Class A Ordinary Shares on July 21, 2026 was $2.69 per share. As of July 21, 2026, the aggregate market value of our outstanding Class A Ordinary Shares held by non-affiliates was $26,826,876.75based upon 7,047,527 outstanding Class A Ordinary Shares, of which 7,041,175 Class A Ordinary Shares were held by non-affiliates,and the last reported sale price of our Class A Ordinary Shares of $3.81 per share on June 1, 2026. Pursuant to General InstructionI.B.5. of Form F-3, in no event will we sell shares pursuant to this prospectus supplement having a value exceeding more than one-third of our public float in any 12-month period so long as our public float remains below $75,000,000. In the event that subsequent tothe date of this prospectus supplement the aggregate market value of our outstanding Class A Ordinary Shares held by non-affiliatesequals or exceeds $75,000,000, such one-third limitation on sales shall not apply to sales subsequently made pursuant to thisprospectus supplement. As of the date hereof, we have sold $2,322,493.74 of securities pursuant to General Instruction I.B.5 of FormF-3 during the 12-calendar month period that ends on and includes the date hereof, and therefore $6,619,798 is available to be soldpursuant to this prospectus supplement. Investing in our securities is highly speculative and involves a high degree of risk. See “Risk Factors” beginning on page S-3 ofthis prospectus supplement and as described in certain of the documents we may incorporate by reference herein, for adiscussion of information that should be considered in connection with an investment in our securities. Neither the Securities and Exchange Commission nor any state or provincial securities commission has approved ordisapproved of these securities or determined if this prospectus supplement is truthful or complete. Any representation to thecontrary is a criminal offense. H.C. Wainwright & Co. The date of this prospectus supplement is July 29, 2026. TABLE OF CONTENTS PageAbout This Prospectus SupplementS-iiProspectus Supplement SummaryS-1The OfferingS-2Risk FactorsS-3Cautionary Note Regarding Forward-Looking StatementsS-4Use of ProceedsS-5Capitalization and IndebtednessS-5DilutionS-7Dividend PolicyS-8Plan of DistributionS-8Legal MattersS-9ExpertsS-9IndemnificationS-10Where You Can Find More Information; Documents Incorporated by ReferenceS-11 BASE PROSPECTUS About This Prospectus1Prospectus Summary2Risk Factors5