C3is (CISS) - Prospectus

Table of Contents As filed with the Securities and Exchange Commission on September 3, 2025. Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 Form F-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 C3IS INC. (Exact name of registrant as specified in its charter) Republic of the Marshall Islands 4412 N/A (State or other jurisdiction of incorporation or organization) (Primary Standard Industrial Classification Code Number) 331 Kifissias Avenue Kifissia 14561 ...