Filed pursuant to Rule 424(b)(3) Registration Statement No. 333-287113 Prospectus Supplement No. 1 (To Prospectus dated May 13, 2025) OKLO INC. This prospectus supplement updates, amends and supplements the prospectus dated May 13, 2025 (the “Prospectus”), which forms a part of our Registration Statement on Form S-1, as amended (Registration No. 333-287113). Capitalized terms used in this prospectus supplement and not otherwise defined herein have the meanings specified in the Prospectus. This prospectus supplement is being filed to update, amend and supplement the information included in the Prospectus with the information contained in our Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2025, filed with the Securities and Exchange Commission on May 13, 2025, which is set forth below. This prospectus supplement is not complete without the Prospectus. This prospectus supplement should be read in conjunction with the Prospectus, which is to be delivered with this prospectus supplement, and is qualified by reference thereto, except to the extent that the information in this prospectus supplement updates or supersedes the information contained in the Prospectus. Please keep this prospectus supplement with your Prospectus for future reference. Oklo Inc.’s Class A Common Stock is quoted on the New York Stock Exchange under the symbol “OKLO.” On May 12, 2025, the closing price of our Class A Common Stock was $28.85. WE ARE AN “EMERGING GROWTH COMPANY” UNDER FEDERAL SECURITIES LAWS AND ARE SUBJECT TO REDUCED PUBLIC REPORTING REQUIREMENTS. INVESTING IN OUR SECURITIES INVOLVES CERTAIN RISKS. SEE “RISK FACTORS” BEGINNING ON PAGE 8 OF THE PROSPECTUS. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if the Prospectus or this prospectus supplement is truthful or complete. Any representation to the contrary is a criminal offense. The date of this prospectus supplement is May 13, 2025.