C3IS Inc. (CISS) consolidates shares with 1-for-20 reverse stock split

Rhea-AI Filing Summary

C3IS Inc. (CISS) has implemented a one-for-20 reverse stock split of its common shares. Effective as of 11:59 p.m. Eastern time on January 25, 2026, every 20 previously issued and outstanding common shares were combined into one new share. This reduced the number of outstanding common shares from approximately 24.7 million to approximately 1.23 million, while leaving the par value and other terms of the common stock unchanged.

No fractional shares were issued; stockholders who would have held a fractional share instead receive a cash payment based on the closing Nasdaq price on the trading day immediately before the effective date, adjusted for the split. The company’s warrants and 5.00% Series A Cumulative Convertible Perpetual Preferred Stock are being proportionately adjusted to increase exercise and conversion prices and reduce the number of shares issuable, with further adjustment of certain Class B-1, B-2, C-1 and C-2 warrants and the Series A conversion price to the lowest daily volume weighted average price over a specified 10-trading-day window around the effective date. C3IS shares continue trading on Nasdaq under the symbol “CISS” with a new CUSIP.

Insights

Equity Structure Analyst

C3IS consolidates its share count via a 1-for-20 reverse split.

C3IS Inc. completed a one-for-20 reverse stock split effective as of January 25, 2026, cutting outstanding common shares from approximately 24.7 million to approximately 1.23 million. This is a capital structure change, not a cash-raising event, and the par value and authorized share counts remain the same.

The filing also details proportional adjustments to outstanding warrants and the 5.00% Series A Cumulative Convertible Perpetual Preferred Stock. Exercise and conversion prices increase, and the number of underlying common shares decreases, with an added feature that the Class B-1, B-2, C-1 and C-2 warrant exercise prices and the Series A conversion price can reset to the lowest daily volume weighted average price during a 10-trading-day window around the effective time. This keeps the aggregate exercise price of these warrants, as of their original issuance, unchanged while aligning instruments with the new share structure.

Fractional entitlements are settled in cash, using the closing price on the Nasdaq Stock Market on the trading day immediately preceding the effective date, as adjusted for the split. Subsequent disclosures may further describe how these warrant and preferred stock adjustments affect potential future issuances of common stock.

UNITED STATES

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 January 2026

Commission File Number 001-41717

C3IS INC.

(Translation of registrant’s name into English)

331 Kifissias Avenue Kifissia 14561 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 ☐

INFORMATION CONTAINED IN THIS FORM 6-K REPORT

Reverse Stock Split

On January 23, 2026, C3is Inc. (the “Company”) filed an amendment to its Restated Articles of Incorporation, to effectuate a reverse stock split of the Company’s issued and outstanding shares of common stock, par value of $0.01 per share. A copy of the amendment is attached hereto as Exhibit 4.1.

Effective as of 11:59 p.m. Eastern time on January 25, 2026, the Company effected a one-for-20 reverse stock split of its shares of common stock, and the Company’s common stock began trading on a split-adjusted basis on The Nasdaq Capital Market as of the opening of trading on January 26, 2026. The reverse stock split reduced the number of outstanding shares of the Company’s common stock from approximately 24.7 million to approximately 1.23 million and affected all outstanding shares of common stock. No fractional shares were issued in connection with the reverse split. Stockholders who would otherwise hold a fractional share of the Company’s common stock received a cash payment in lieu of such fractional share. The Company’s outstanding warrants and Series A Convertible Preferred Stock will be proportionately adjusted to increase the exercise price and reduce the number of shares issuable upon exercise to reflect the reverse stock split.

The exercise price of the Class B-1, B-2, C-1 and C-2 Warrants, and accordingly the conversion price of the Series A Convertible Preferred Stock, will be further adjusted to the lowest daily volume weighted average price during the period commencing five consecutive trading days immediately preceding and the five consecutive trading days following the effective time of the reverse split (if lower than the then current exercise price), with the Class B-1 and C-1 warrants also being exercisable pursuant to an alternative zero cash exercise exchange option, and the number of shares of common stock issuable upon exercise will be proportionately adjusted such that the aggregate exercise price of such warrants as of their original issuance date will remain unchanged.

The par value and other terms of the Company’s shares of common stock were not affected by the reverse stock split. The Company’s post-reverse split common shares have a new CUSIP number, Y18284 177, and continue to trade on the Nasdaq Capital Market under the symbol “CISS”.

A copy of the new form of stock certificate for the Company’s post-reverse stock split shares of common stock is attached hereto as Exhibit 4.2.

*****

This report on Form 6-K is hereby incorporated by reference into the Company’s Registration Statement on Form S-8 (Reg. No. 333-273306) filed with the Securities and Exchange Commission on July 18, 2023 and Registration Statement on Form F-3 (Reg. No. 333- 285135) filed with the Securities and Exchange Commission on February 21, 2025.

EXHIBIT INDEX

4.1		Articles of Amendment to Restated Articles of Incorporation.
4.2		Form of Common Stock Certificate.

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.

Date: January 26, 2026

C3IS INC.

By:		/s/ Nina Pyndiah
Name:		Nina Pyndiah
Title:		Chief Financial Officer

Exhibit 4.1

ARTICLES OF AMENDMENT

TO

AMENDED AND RESTATED ARTICLES OF INCORPORATION

OF

C3IS INC.

Under Section 90 of the

Republic of the Marshall Islands Business Corporations Act

C3IS INC., a corporation incorporated in and existing under the law of the Republic of the Marshall Islands (the “Corporation”), hereby certifies as follows:

(a) The name of the Corporation is: C3IS INC.

(b) The Corporation was originally incorporated by filing Articles of Incorporation in the Republic of The Marshall Islands on July 25, 2022. Amended and Restated Articles of Incorporation were filed with the Registrar of Corporations of the Republic of the Marshall Islands on June 13, 2023, as amended by the Articles of Amendment filed with the Registrar of Corporations of the Republic of the Marshall Islands on April 11, 2024, December 31, 2024, and April 3, 2025 (as so amended, restated and corrected, the “Articles of Incorporation”). A Statement of Designation was filed pursuant to Section 35(5) of the Business Corporations Act on June 20, 2023 in respect to the rights, preferences and privileges of the 5.00% Series A Cumulative Convertible Perpetual Preferred Stock of the Corporation.

(c) The Amended and Restated Articles of Incorporation are hereby amended by inserting the following as a new paragraph into Section FOURTH immediately following the last paragraph therein:

(g) 2026 Reverse Stock Split. As of 11:59 p.m. Eastern time on January 25, 2026 (the “2026 Reverse Stock Split Effective Date”), each twenty (20) shares of Common Stock issued and outstanding immediately prior to the 2026 Reverse Stock Split Effective Date either issued and outstanding or held by the Corporation as treasury stock shall be combined into one (1) validly issued, fully paid and non-assessable share of Common Stock without any further action by the Corporation or the holder thereof (the “2026 Reverse Stock Split”); provided that no fractional shares shall be issued to any holder and that in lieu of issuing any such fractional shares, fractional shares resulting from the 2026 Reverse Stock Split will be rounded down to the nearest whole share and provided, further, that stockholders who would otherwise be entitled to receive fractional shares because they hold a number of shares not evenly divisible by the ratio of the 2026 Reverse Stock Split will receive a cash payment (without interest and subject to applicable withholding taxes) in an amount per share equal to the closing price per share of Common Stock on the Nasdaq Stock Market on the trading day immediately preceding the 2026 Reverse Stock Split Effective Date, as adjusted for the reverse stock split as appropriate. Each certificate, if any, that immediately prior to the 2026 Reverse Stock Split Effective Date represented shares of Common Stock (“Old Certificates”), shall thereafter represent that number of shares of Common Stock into which the shares of Common Stock represented by the Old Certificate shall have been combined, subject to the elimination of fractional shares as described above. The reverse stock split described in this paragraph shall not change the number of shares of Common Stock

authorized to be issued or the par value of the Common Stock. No change was made to the number of registered shares of Preferred Stock the Corporation is authorized to issue or to the par value of the Preferred Stock.

(d) This amendment to the Amended and Restated Articles of Incorporation was authorized by actions of the Board of Directors and shareholders of the Corporation as required by the BCA.

IN WITNESS WHEREOF, the Corporation has caused these Articles of Amendment to Amended and Restated Articles of Incorporation to be signed as of the 23rd day of January, 2026, by its Chief Executive Officer, who hereby affirms and acknowledges, under penalty of perjury, that these Articles of Amendment are the act and deed of the Corporation and that the facts stated herein are true.

C3IS INC.
By:		/s/ Diamantis Andriotis
		Name: Diamantis Andriotis
		Title:  Chief Executive Officer

FAQ

What did C3IS Inc. (CISS) announce in its January 2026 Form 6-K?

C3IS Inc. implemented a one-for-20 reverse stock split of its common stock, effective as of 11:59 p.m. Eastern time on January 25, 2026, and adjusted related warrants and preferred stock accordingly.

How did the reverse stock split change C3IS (CISS) shares outstanding?

The reverse stock split reduced outstanding common shares from approximately 24.7 million to approximately 1.23 million, by combining every 20 existing shares into one new share.

How are fractional shares handled in the C3IS (CISS) reverse split?

No fractional shares are issued. Stockholders who would otherwise receive a fractional share instead get a cash payment based on the closing price of the common stock on Nasdaq on the trading day immediately before the effective date, adjusted for the reverse split.

What happens to C3IS Inc.’s warrants and Series A Convertible Preferred Stock after the reverse split?

Outstanding warrants and 5.00% Series A Cumulative Convertible Perpetual Preferred Stock are proportionately adjusted so that exercise and conversion prices increase and the number of shares issuable decreases, with certain Class B-1, B-2, C-1 and C-2 warrants and the Series A conversion price further adjustable to the lowest daily volume weighted average price over a specified 10-trading-day period.

Did the C3IS (CISS) reverse stock split change the par value or authorized share counts?

The reverse stock split did not change the par value of the common stock or the number of authorized common or preferred shares the company may issue.

Does C3IS Inc. (CISS) have a new CUSIP or ticker after the reverse split?

Post-reverse-split common shares have a new CUSIP number Y18284 177, but they continue to trade on the Nasdaq Capital Market under the symbol “CISS”.

How is this C3IS (CISS) reverse split reflected in other SEC registrations?

The Form 6-K is incorporated by reference into C3IS Inc.’s Registration Statement on Form S-8 (Reg. No. 333-273306) and Registration Statement on Form F-3 (Reg. No. 333-285135).