克瑞拓斯安全防卫美股招股说明书(2026-04-17版)

This prospectus supplement supplements information contained in that certain prospectus dated February 26, 2026 filed as part ofthat certain registration statement on Form S-3 filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 26,2026 and relates to the offer and sale from time to time by the selling stockholders named herein of up to 14,768 shares of the commonstock, par value $0.001 per share (the “common stock”), of Kratos Defense & Security Solutions, Inc. (the “Company”). We areregistering the resale of the shares of common stock covered by this prospectus supplement as required by the terms of the Agreementand Plan of Merger that we entered into with the selling stockholders and the other parties named therein on February 11, 2026 (the“Merger Agreement”). Our registration of the shares of common stock covered by this prospectus supplement does not mean that the selling stockholderswill offer or sell any of the shares. The selling stockholders may offer and sell or otherwise dispose of the shares of common stockdescribed in this prospectus supplement from time to time through public or private transactions at prevailing market prices, at pricesrelated to prevailing market prices or at privately negotiated prices. See “Plan of Distribution” beginning on pageS-15for moreinformation. We will not receive any of the proceeds from the sale of shares of common stock by the selling stockholders. The sellingstockholders will pay all underwriting discounts and selling commissions, if any, in connection with the sale of the shares of commonstock. We have agreed to pay certain expenses in connection with this prospectus supplement. As of the date of this prospectussupplement, no underwriter or other person has been engaged to facilitate the sale of shares of common stock in this offering. You should read this prospectus supplement, any subsequent, applicable prospectus supplement and any related free writingprospectus carefully before you invest. Our common stock is listed on The Nasdaq Global Select Market under the symbol “KTOS.” On April 16, 2026, the last reportedsale price of our common stock on The Nasdaq Global Select Market was $74.41. Investing in our securities involves various risks anduncertainties. You should carefully review the risks and uncertainties described under the heading “Risk Factors” beginning on pageS-7and contained under similar headings in the other documents that we incorporate by reference into this prospectus supplement. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or determined if this prospectus supplement is truthful or complete. Any representation to the contrary is acriminal offense. The date of this prospectus supplement is April 17, 2026. TABLE OF CONTENTS Prospectus Supplement ABOUT THIS PROSPECTUS SUPPLEMENTTRADEMARKS, SERVICE MARKS AND TRADENAMESMARKET AND INDUSTRY DATAPROSPECTUS SUPPLEMENT SUMMARYRISK FACTORSSPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATIONUSE OF PROCEEDSDIVIDEND POLICYTHE SELLING STOCKHOLDERSPLAN OF DISTRIBUTIONMATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES TO NON-U.S. HOLDERSCERTAIN ERISA CONSIDERATIONSVALIDITY OF SECURITIESEXPERTSWHERE YOU CAN FIND ADDITIONAL INFORMATIONINCORPORATION OF CERTAIN INFORMATION BY REFERENCE Prospectus ABOUT THIS PROSPECTUSSUMMARYRISK FACTORSFORWARD-LOOKING STATEMENTSUSE OF PROCEEDSSELLING SECURITY HOLDERSPLAN OF DISTRIBUTIONDESCRIPTION OF CAPITAL STOCKDESCRIPTION OF DEBT SECURITIESDESCRIPTION OF WARRANTSDESCRIPTION OF RIGHTSDESCRIPTION OF UNITSLEGAL OWNERSHIP OF SECURITIESLEGAL MATTERSEXPERTSWHERE YOU CAN FIND ADDITIONAL INFORMATIONINCORPORATION OF CERTAIN INFORMATION BY REFERENCE ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplement and the accompanying prospectus are part of an automatic shelf registration statement that we filedwith the Securities and Exchange Commission (“SEC”), as a “well-known seasoned issuer” as defined in Rule 405 under theSecurities Act of 1933, as amended (the “Securities Act”), utilizing a “shelf” registration process. This document is in two parts. Thefirst part is this prospectus supplement, including the documents incorporated by reference, which describes the specific terms of thisoffering. The second part, the accompanying prospectus, including the documents incorporated by reference, provides more generalinformation. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. We urge you tocarefully read this prospectus supplement and the accompanying prospectus, and the documents incorporated by reference herein andtherein, before buying any of the securities being offered under this prospectus supplement. This prospectus supplement may add to orupdate information contained in the accompanying prospectus and the documents incorporated by reference therein. To the extent thatany statement we make in this prospectus supp