The 1921 Idaho Vandals football team represented the University of Idaho in the 1921 college football season. Idaho was led by second-year head coach Thomas Kelley in their last season as an independent before joining the Pacific Coast Conference. The Vandals had two home games in Moscow, one on campus at MacLean Field and another at the fairgrounds; they also played one in Boise at Public School Field. The Boise game against Wyoming on the third anniversary of Armistice Day was attended by Governor D. W. Davis.