A10 Networks Inc美股招股说明书(2026-08-07版)

153,962 Shares of Common Stock This prospectus supplement relates to the offer and sale from time to time of up to 153,962 of shares (the “Shares”) of common stock, par value$0.00001 per share (“Common Stock”), of A10 Networks, Inc. (“we,” the “Company” or “A10”) by the selling stockholders listed in the section of thisprospectus supplement entitled “Selling Stockholders”, or their donees, pledgees, transferees, or other successors in interest, including those who receiveany of the shares as a gift, pledge, distribution, redemption, repurchase, cancellation, or other non-sale related transfer (the “Selling Stockholders”). TheShares were issued by us to the Selling Stockholders on June15, 2026 as partial consideration for our acquisition of all of the outstanding shares ofTrojAI Inc., a corporation incorporated under the Canada Business Corporations Act (the “Target”), pursuant to a Share Purchase Agreement, dated as ofJune12, 2026, by and among A10 Networks Canada Inc., a corporation incorporated under the Business Corporations Act (Ontario) and a wholly ownedsubsidiary of the Company (the “Buyer”), the Company, the Target, the shareholders of the Target (including the Selling Stockholders) and ShareholderRepresentative Services LLC, a Colorado limited liability company, as seller representative (the “Share Purchase Agreement”). Our registration for resale of the Shares covered by this prospectus supplement does not mean that the Selling Stockholders will offer or sell anyof the Shares. The Selling Stockholders may sell the Shares covered by this prospectus supplement in a number of different ways and at varying prices.For additional information on the possible methods of sale that may be used by the Selling Stockholders, you should refer to the section of thisprospectus supplement entitled “Plan of Distribution” beginning on pageS-10of this prospectus supplement. We will not receive any of the proceedsfrom the sale of Shares by the Selling Stockholders. The Selling Stockholders will bear all commissions and discounts, if any, attributable to their sale ofShares. Our Common Stock is listed on the New York Stock Exchange (the “NYSE”) under the symbol “ATEN.” On August5, 2026, the last reported saleprice of our Common Stock on the NYSE was $30.84 per share. Investing in our Common Stock involves a high degree of risk. You should review carefully the risks and uncertaintiesdescribed in the section entitled “Risk Factors” contained on pageS-3of this prospectus supplement as well as anyother risk factors and information contained in any other documents that are incorporated by reference herein ortherein. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities ordetermined if this prospectus supplement and the accompanying prospectus are truthful or complete. Any representation to the contrary is acriminal offense. The securities are not being offered in any jurisdiction where the offer is not permitted. TABLE OF CONTENTS PROSPECTUS SUPPLEMENT ABOUT THIS PROSPECTUS SUPPLEMENTTHE COMPANYRISK FACTORSDISCLOSURE REGARDING FORWARD-LOOKING STATEMENTSUSE OF PROCEEDSSELLING STOCKHOLDERSPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTSWHERE YOU CAN FIND MORE INFORMATIONINCORPORATION OF CERTAIN INFORMATION BY REFERENCE PROSPECTUS ABOUT THIS PROSPECTUSRISK FACTORSA10 NETWORKS, INC.FORWARD-LOOKING STATEMENTSUSE OF PROCEEDSDESCRIPTION OF DEBT SECURITIESDESCRIPTION OF CAPITAL STOCKDESCRIPTION OF DEPOSITARY SHARESDESCRIPTION OF WARRANTSFORMS OF SECURITIESSELLING SECURITYHOLDERSPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTSWHERE YOU CAN FIND MORE INFORMATION ABOUT THIS PROSPECTUS SUPPLEMENT You should rely only on the information contained or incorporated by reference into this prospectus supplement and the accompanying prospectus. Wehave not authorized anyone to provide you with information different from that contained in this prospectus supplement, the accompanying prospectusand any free writing prospectus prepared by on behalf of us and the selling stockholders or any information incorporated by reference herein and therein.No dealer, salesperson or other person is authorized to give any information or to represent anything not contained in this prospectus supplement or theaccompanying prospectus. You should not rely on any unauthorized information or representation. This prospectus supplement and the accompanying prospectus is an offer to sell only the securities offered hereby and thereby, but only undercircumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus supplement and theaccompanying prospectus is accurate only as of the date on the front of the document and that any information we have incorporated by reference isaccurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus supplement and theaccompanying prospectus or