William Cowan may refer to:
- William Cowan (footballer born 1900) (1900–1979), English footballer
- William Cowan (fur trader) (1818–1902), of the Hudson's Bay Company
- William Cowan (politician) (1825–?), reeve of North Gower Township, Ontario
- William Henry Cowan, Scottish politician
- Bill Cowan (born 1943), security expert
- Billy Cowan (born 1938), retired baseball player
- Billy Cowan (footballer) (1896–?), Scottish footballer