Document and Entity Information	12 Months Ended
	Dec. 31, 2019 shares
Document and Entity Information [Abstract]
Document Type	20-F
Document Registration Statement	false
Document Annual Report	true
Document Transition Report	false
Document Shell Company Report	false
Entity Registrant Name	The9 LTD
Document Period End Date	Dec. 31, 2019
Entity Incorporation, State or Country Code	F4
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding	121,761,675
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0001296774
Amendment Flag	false
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Trading Symbol	NCTY