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SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER

PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of August 2026

Commission File Number: 001-42684

Rubico Inc.

(Translation of registrant's name into English)

20 Iouliou Kaisara Str

19002, Paiania

Athens – Greece

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F     ☒          Form 40-F     ☐

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INFORMATION CONTAINED IN THIS REPORT ON FORM 6-K

Attached as Exhibit 99.1 to this Report on Form 6-K (this “Report”) is Management’s Discussion and Analysis of Financial Condition and Results of Operations for the Six Months Ended June 30, 2025 and 2026 and the interim unaudited condensed consolidated financial statements, and the accompanying notes thereto, for the six months ended June 30, 2026, of Rubico Inc.

The information contained in this Report is hereby incorporated by reference into the Registrant’s registration statement on Form F-3 (File No. 333-297207).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

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