C3is (CISS) - Prospectus(update)

Table of Contents As filed with the Securities and Exchange Commission on December 5, 2025. Registration No. 333-290011 UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 Amendment No. 2 To 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) Puglisi & Associates 850 Library Avenue, Suite 204 Newark, Delaware ...