v3.25.1
Cover Page
 12 Months Ended
Dec. 31, 2024
shares
Document Information [Line Items]  
Document Type 20-F
Entity Registrant Name C3IS INC.
Entity Central Index Key 0001951067
Document Period End Date Dec. 31, 2024
Amendment Flag false
Current Fiscal Year End Date --12-31
Entity Well-known Seasoned Issuer No
Entity Voluntary Filers No
Entity Filer Category Non-accelerated Filer
Entity Current Reporting Status Yes
Entity Emerging Growth Company true
Entity Ex Transition Period true
Title of 12(b) Security Common Stock, par value $0.01 per share
Trading Symbol CISS
Security Exchange Name NASDAQ
Entity Shell Company false
Document Fiscal Year Focus 2024
Document Fiscal Period Focus FY
Document Annual Report true
Document Transition Report false
Entity Interactive Data Current Yes
Document Accounting Standard U.S. GAAP
Document Shell Company Report false
Securities Act File Number 001-41717
Entity Incorporation, State or Country Code 1T
Document Registration Statement false
Entity Address, Address Line One 331 Kifissias Avenue
Entity Address, Address Line Two Erithrea
Entity Address, City or Town Athens
Entity Address, Postal Zip Code 14561
Entity Address, Country GR
Contact Personnel Fax Number 625 0018
Auditor Location Athens, Greece
Auditor Firm ID 1163
Auditor Name Deloitte Certified Public Accountants S.A.
ICFR Auditor Attestation Flag false
Document Financial Statement Error Correction [Flag] false
Business Contact [Member]  
Document Information [Line Items]  
Contact Personnel Name Dr. Diamantis Andriotis
Entity Address, Address Line One 331 Kifissias Avenue
Entity Address, Address Line Two Erithrea
Entity Address, City or Town Athens
Entity Address, Postal Zip Code 14561
Entity Address, Country GR
Country Region 30
City Area Code 210
Local Phone Number 625 0001
Common Stock [Member]  
Document Information [Line Items]  
Entity Common Stock, Shares Outstanding 706,500
Series A Convertible Preferred Stock [Member]  
Document Information [Line Items]  
Entity Common Stock, Shares Outstanding 600,000