v3.26.1
Document and Entity Information - shares
 9 Months Ended
Jun. 30, 2026
Aug. 11, 2026
Document and Entity Information    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2026  
Document Transition Report false  
Entity File Number 000-56605  
Entity Registrant Name Gouverneur Bancorp, Inc.  
Entity Incorporation, State or Country Code MD  
Entity Tax Identification Number 37-2102925  
Entity Address, Address Line One 42 Church Street  
Entity Address, City or Town Gouverneur  
Entity Address State Or Province NY  
Entity Address, Postal Zip Code 13642  
City Area Code 315  
Local Phone Number 287-2600  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   1,058,922
Entity Central Index Key 0001978811  
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q3  
Amendment Flag false