<SEC-DOCUMENT>0000898432-25-000848.txt : 20251028
<SEC-HEADER>0000898432-25-000848.hdr.sgml : 20251028
<ACCEPTANCE-DATETIME>20251028170051
ACCESSION NUMBER:		0000898432-25-000848
CONFORMED SUBMISSION TYPE:	SCHEDULE 13G
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20251028
DATE AS OF CHANGE:		20251028

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 13G
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	005-94125
		FILM NUMBER:		251425700

	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:			Athanasios Tsiakmakis
		CENTRAL INDEX KEY:			0002093911
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		SCHEDULE 13G

	MAIL ADDRESS:	
		ADDRESS IS A NON US LOCATION: 	YES
		STREET 1:		RODOPIS 35 GLUFADA
		CITY:			ATHENS
		PROVINCE COUNTRY:   	J3
		ZIP:			00000
</SEC-HEADER>
<DOCUMENT>
<TYPE>SCHEDULE 13G
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
<XML>
<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/schedule13g" xmlns:com="http://www.sec.gov/edgar/common">
<headerData>
<submissionType>SCHEDULE 13G</submissionType>
<filerInfo>
<filer>
<filerCredentials>
<cik>0002093911</cik>
<ccc>XXXXXXXX</ccc>
</filerCredentials>
</filer>
<liveTestFlag>LIVE</liveTestFlag>



</filerInfo>
</headerData>
<formData>
<coverPageHeader>
<securitiesClassTitle>Common Stock, par value $0.01 per share</securitiesClassTitle>
<eventDateRequiresFilingThisStatement>09/16/2025</eventDateRequiresFilingThisStatement>
<issuerInfo>
<issuerCik>0001951067</issuerCik>
<issuerName>C3is Inc.</issuerName>
<issuerCusip>Y18284169</issuerCusip>
<issuerPrincipalExecutiveOfficeAddress>
<com:street1>331 Kifissias Avenue</com:street1>
<com:street2>Kifissia</com:street2>
<com:city>Athens</com:city>
<com:stateOrCountry>J3</com:stateOrCountry>
<com:zipCode>14561</com:zipCode>
</issuerPrincipalExecutiveOfficeAddress>
</issuerInfo>
<designateRulesPursuantThisScheduleFiled>
<designateRulePursuantThisScheduleFiled>Rule 13d-1(c)</designateRulePursuantThisScheduleFiled>
</designateRulesPursuantThisScheduleFiled>
</coverPageHeader>
<coverPageHeaderReportingPersonDetails>

<reportingPersonName>Athanasios Tsiakmakis</reportingPersonName>
<citizenshipOrOrganization>J3</citizenshipOrOrganization>
<reportingPersonBeneficiallyOwnedNumberOfShares>
<soleVotingPower>155000</soleVotingPower>
<sharedVotingPower>0</sharedVotingPower>
<soleDispositivePower>155000</soleDispositivePower>
<sharedDispositivePower>0</sharedDispositivePower>
</reportingPersonBeneficiallyOwnedNumberOfShares>
<reportingPersonBeneficiallyOwnedAggregateNumberOfShares>155000</reportingPersonBeneficiallyOwnedAggregateNumberOfShares>
<aggregateAmountExcludesCertainSharesFlag>N</aggregateAmountExcludesCertainSharesFlag>
<classPercent>14.36</classPercent>
<typeOfReportingPerson>IN</typeOfReportingPerson>
<comments>Ownership as of October 27, 2025. See Item 4(b) for additional details.</comments>
</coverPageHeaderReportingPersonDetails>
<items>
<item1>
<issuerName>C3is Inc.</issuerName>
<issuerPrincipalExecutiveOfficeAddress>331 Kifissias Avenue, Kifissia, Athens, Greece, 14561</issuerPrincipalExecutiveOfficeAddress>
</item1>
<item2>
<filingPersonName>Athanasios Tsiakmakis</filingPersonName>
<principalBusinessOfficeOrResidenceAddress>The address of the principal business office of the Reporting Person is Dimokratias 17, Agioi Anargyroi, Athens.</principalBusinessOfficeOrResidenceAddress>
<citizenship>Greece</citizenship>
</item2>
<item3>
<notApplicableFlag>Y</notApplicableFlag>
</item3>
<item4>
<amountBeneficiallyOwned>The information required by Item 4(a) is set forth in Row 9 of the cover page and is incorporated herein by reference.</amountBeneficiallyOwned>
<classPercent>The information required by Item 4(b) is set forth in Row 11 of the cover page and is incorporated herein by reference.&#13;
&#13;
The information in Row 11 is calculated on the basis of 1,079,208 shares of Common Stock issued and outstanding as of August 31,2025, as reported by the Issuer in the Form F-1 Registration Statement filed by the Issuer with the Securities and Exchange Commission on September 3, 2025.&#13;
&#13;
As of the date of event that required the filing of this Schedule 13G, the Reporting Person may have been deemed to beneficially own more than 5% of the outstanding shares of Common Stock. As of September 17, 2025, the Reporting Person may have been deemed to beneficially own more than 10% of the outstanding shares of Common Stock.</classPercent>
<numberOfSharesPersonHas>
<solePowerOrDirectToVote>The information required by Item 4(c)(i) is set forth in Row 5 of the cover page and is incorporated herein by reference.</solePowerOrDirectToVote>
<sharedPowerOrDirectToVote>The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page and is incorporated herein by reference.</sharedPowerOrDirectToVote>
<solePowerOrDirectToDispose>The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page and is incorporated herein by reference.</solePowerOrDirectToDispose>
<sharedPowerOrDirectToDispose>The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page and is incorporated herein by reference.</sharedPowerOrDirectToDispose>
</numberOfSharesPersonHas>
</item4>
<item5>
<notApplicableFlag>Y</notApplicableFlag>
</item5>
<item6>
<notApplicableFlag>Y</notApplicableFlag>
</item6>
<item7>
<notApplicableFlag>Y</notApplicableFlag>
</item7>
<item8>
<notApplicableFlag>Y</notApplicableFlag>
</item8>
<item9>
<notApplicableFlag>Y</notApplicableFlag>
</item9>
<item10>
<notApplicableFlag>N</notApplicableFlag>
<certifications>By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.</certifications>
</item10>
</items>
<signatureInformation>
<reportingPersonName>Athanasios Tsiakmakis</reportingPersonName>
<signatureDetails>
<signature>/s/ Athanasios Tsiakmakis</signature>
<title>Athanasios Tsiakmakis</title>
<date>10/28/2025</date>
</signatureDetails>
</signatureInformation>
</formData>
</edgarSubmission>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
