GCT半导体控股有限公司美国存托凭证招股说明书（2026年6月18日版）

Up to $120,000,000 of Common Stock We have previously entered into an At Market Issuance Sales Agreement (the “sales agreement”) dated April 1, 2025, with B.Riley Securities, Inc. and H.C. Wainwright & Co., LLC (the “sales agents”), as our sales agents, relating to shares of our commonstock, par value $0.0001 per share (“Common Stock”). We are filing this prospectus supplement to reflect an increase in our existing atthe market offering program to allow for the issuance of an additional $45.0 million in shares of our Common Stock pursuant to the Sales of our Common Stock, if any, under this prospectus will be made by any method that is deemed to be an “at the marketoffering” as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended (the “Securities Act”). Our Common Stock islisted on The New York Stock Exchange (“NYSE”) under the symbol “GCTS.” The last reported sale price of our Common Stock on The compensation of our sales agents for sales of Common Stock pursuant to the sales agreement shall be a commission rateup to 3.0% of the gross proceeds from each sale. The net proceeds from any sale under this prospectus will be used as described under In connection with the sale of the Common Stock on our behalf, each sales agent will be deemed to be an “underwriter”within the meaning of the Securities Act, and the compensation of the sales agents will be deemed to be underwriting commissions ordiscounts. We have also agreed to provide indemnification and contribution to the sales agents with respect to certain civil liabilities, The sales agents are not required to sell any specific number or dollar amount of Common Stock but will use theircommercially reasonable efforts, as our agents and subject to the terms of the sales agreement, to sell the Common Stock offered, asinstructed by us. The offering of Common Stock pursuant to this prospectus will terminate upon the earlier of (i) the sale of all We are an “emerging growth company” under federal securities laws and are subject to reduced public company reportingrequirements. Investing in our Common Stock involves a high degree of risk. See “Risk Factors” beginning on page 4 of thisprospectus and the “Risk Factors” section contained in our reports filed with the Securities and Exchange Commission which are Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminaloffense. H.C. Wainwright & Co. B. Riley Securities The date of this prospectus supplement is June 18, 2026. TABLE OF CONTENTS ABOUT THIS PROSPECTUS SUPPLEMENTS-1PROSPECTUS SUPPLEMENT SUMMARYS-2 Prospectus ABOUT THIS PROSPECTUSPROSPECTUS SUMMARYRISK FACTORSWHERE YOU CAN FIND MORE INFORMATIONDOCUMENTS INCORPORATED BY REFERENCECAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTSUSE OF PROCEEDSDESCRIPTION OF COMMON STOCKDESCRIPTION OF PREFERRED STOCKDESCRIPTION OF WARRANTSDESCRIPTION OF DEBT SECURITIESDESCRIPTION OF RIGHTSDESCRIPTION OF UNITSPLAN OF DISTRIBUTIONLEGAL MATTERSEXPERTS The distribution of this prospectus supplement and sale of these securities in certain jurisdictions may be restricted.Persons in possession of this prospectus supplement are required to inform themselves about and observe any such restrictions.We are not making an offer of these securities in any jurisdiction where the offer is not permitted. ABOUT THIS PROSPECTUS SUPPLEMENT This document is in two parts. The first part is this prospectus supplement, which contains specific information about theterms on which we are offering and selling our Common Stock and also adds to and updates information contained in theaccompanying prospectus and documents incorporated by reference herein and therein. Under this prospectus supplement and theaccompanying prospectus, we may offer and sell shares of our common stock having an aggregate offering price of up to$120,000,000 from time to time through or to the sales agents at prices and on terms to be determined by market conditions at the timeof the offering. The second part is the accompanying prospectus, which contains and incorporates by reference more generalinformation, some of which may not apply to this offering. This prospectus supplement and the accompanying prospectus are part of aregistration statement on Form S-3 that we filed with the U.S. Securities and Exchange Commission (the “SEC”) using a “shelf” We have not, and the sales agents have not, authorized anyone to provide you with information other than the information thatwe have provided or incorporated by reference in this prospectus supplement, the accompanying base prospectus or any otherprospectus supplement and your reliance on any unauthorized information or representation is at your own risk. This prospectussupplement may be used only in jurisdictions where offers and sales of these securities are permitted. You sh