# EDGAR Filing Document

**Accession Number:** 0001876581
**File Stem:** 0001193125-25-237181
**Filing Date:** 2025-10
**Character Count:** 9297
**Document Hash:** 50ed450263a7241de140bf64170edf4a
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-237181.hdr.sgml**: 20251010

**ACCESSION NUMBER**: 0001193125-25-237181

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20251010

**DATE AS OF CHANGE**: 20251010

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** C3is Inc.
- **CENTRAL INDEX KEY:** 0001951067
- **STANDARD INDUSTRIAL CLASSIFICATION:** DEEP SEA FOREIGN TRANSPORTATION OF FREIGHT [4412]
- **ORGANIZATION NAME:** 01 Energy & Transportation
- **EIN:** 000000000
- **STATE OF INCORPORATION:** 1T
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-94125
- **FILM NUMBER:** 251388626

**BUSINESS ADDRESS:**
- **STREET 1:** 331 KIFISSIAS AVENUE
- **STREET 2:** ERITHREA
- **CITY:** ATHENS
- **STATE:** J3
- **ZIP:** 14561
- **BUSINESS PHONE:** 011-30-210-625-0001

**MAIL ADDRESS:**
- **STREET 1:** 331 KIFISSIAS AVENUE
- **STREET 2:** ERITHREA
- **CITY:** ATHENS
- **STATE:** J3
- **ZIP:** 14561
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Imperial Petroleum Inc./Marshall Islands
- **CENTRAL INDEX KEY:** 0001876581
- **STANDARD INDUSTRIAL CLASSIFICATION:** DEEP SEA FOREIGN TRANSPORTATION OF FREIGHT [4412]
- **ORGANIZATION NAME:** 01 Energy & Transportation
- **EIN:** 000000000
- **STATE OF INCORPORATION:** 1T
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A

**BUSINESS ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** 331 KIFISSIAS AVENUE
- **STREET 2:** ERITHREA
- **CITY:** ATHENS
- **PROVINCE COUNTRY:** J3
- **BUSINESS PHONE:** 011 30 210 625 2849

**MAIL ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** 331 KIFISSIAS AVENUE
- **STREET 2:** ERITHREA
- **CITY:** ATHENS
- **PROVINCE COUNTRY:** J3

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**(Amendment No. 6)**

**C3is Inc.**

*(Name of Issuer)*

**Common Stock, par value $0.01 per share**

*(Title of Class of Securities)*

**Y18284169**

*(CUSIP Number)*

**Harry N. Vafias**<br>331 Kifissias Avenue<br>Kifissia<br>Athens J3 14561<br>011 30210 625 0001

*(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)*

**10/09/2025**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **Y18284169** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Imperial Petroleum Inc.** | Name of reporting person<br>**Imperial Petroleum Inc.** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**OO** | Source of funds (See Instructions)<br>**OO** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**1T** | Citizenship or place of organization<br>**1T** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**6000000.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**6000000.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**6000000.00** | Aggregate amount beneficially owned by each reporting person<br>**6000000.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**68.8%** | Percent of class represented by amount in Row (11)<br>**68.8%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common Stock, par value $0.01 per share

**(b) Name of Issuer:**
C3is Inc.

**(c) Address of Issuer's Principal Executive Offices:**
331 Kifissias Avenue, Kifissia, Athens, J3, 14561

This Amendment No. 6 (this "Amendment No. 6") to Schedule 13D (originally filed on July 28, 2023 and amended by Amendment No. 1 filed on January 24, 2024, Amendment No. 2 filed on March 20, 2024, Amendment No. 3 filed on May 1, 2024, Amendment No. 4 on January 14, 2025 and Amendment No. 5 filed on April 15, 2025), relates to the common stock, par value $0.01 per share ("Common Stock"), of C3is Inc., a Marshall Islands corporation (the "Issuer"), and is being filed by Imperial Petroleum Inc., a Marshall Islands corporation ("Imperial Petroleum" or the "Reporting Person").

Information given in response to each item below shall be deemed incorporated by reference in all other items below. Unless indicated otherwise, all items left blank remain unchanged, and any items which are amended below are deemed to amend and update the existing items in the Schedule 13D.

**Item 4. Purpose of Transaction**

The Reporting Person involved in the securities described in this Schedule 13D in connection with the Spin-Off Distribution, and intends to review its investment in the Issuer on a continuing basis. The Reporting Person may from time to time acquire additional securities of the Issuer, or retain or sell all or portion of the shares then held by the Reporting Person, in the open market, block trades, underwritten public offerings or privately negotiated transactions. Any actions the Reporting Person might undertake with respect to its investment in the Issuer may be made at any time and from time to time and will be dependent upon the Reporting Person's review of numerous factors, including, but not limited to: ongoing evaluation of the Issuer's business, financial condition, operations, prospects and strategic alternatives; price levels of the Issuer's securities; general market, industry and economic conditions; the relative attractiveness of alternative business and investment opportunities; tax considerations; liquidity of the Issuer's securities; and other factors and future developments.

Mr. Vafias serves as the Non-Executive Chairman of the Issuer and John Kostoyannis and George Xiradakis each serve as a director of the Issuer, other shareholders of the Issuer and other relevant parties, which discussions may include matters ranging from the operations and conduct of the Issuer's business to considering or exploring extraordinary corporate transactions including the events listed in Item 4(a) through 4(j) of Schedue 13D. In connection with these discussions, the Reporting Person may, either directly or through one or more affiliates, determine to take any available course of action or to take no course of action and may at any time and from time to time take steps to further or implement such course of action, including any of the events listed in Item 4(a) through 4(j) of Schedule 13D. Any action or actions the Reporting Person may undertake with respect to its investment in the Issuer or the operations and conduct of the Issuer's business will be dependent upon the Reporting Person's review of numerous factors, including those listed above, and the Reporting Person specifically reserves the right to change its intentions, or to formulate plans and proposals, with respect to any or all of the matters described in this paragraph, subject to applicable law and regulations.

**Item 5. Interest in Securities of the Issuer**

**(a)**
The responses of Imperial Petroleum to Rows (7) through (11) of the cover page of this Schedule are incorporated herein by reference. Except as set forth herein, neither Imperial Petroleum nor, to the knowledge of Imperial Petroleum, the Covered Persons beneficially own any Common Stock as of the date of this filing.

**(b)**
The responses of Imperial Petroleum to Rows (7) through (11) of the cover page of this Schedule are incorporated herein by reference. Except as set forth herein, neither Imperial Petroleum nor, to the knowledge of Imperial Petroleum, the Covered Persons beneficially own any Common Stock as of the date of this filing.

**(c)**
The information set forth in Item 3 is hereby incorporated herein by reference. Other than as set forth in this Schedule, neither Imperial Petroleum nor, to the best of its knowledge, any of the Covered Persons has engaged in any transaction in any Common Stock during the past 60 days.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Imperial Petroleum Inc.

**Signature:** Harry N. Vafias

**Name/Title:** Chief Executive Officer

**Date:** 10/10/2025