Document and Entity Information	12 Months Ended
	Dec. 31, 2020
Cover [Abstract]
Entity Registrant Name	DENISON MINES CORP.
Entity Central Index Key	0001063259
Document Type	6-K
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020