1921 Idaho Vandals football team

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.

Idaho dropped a seventh consecutive game to Washington State in the Battle of the Palouse, falling 3–20 at Rogers Field in Pullman. Two years later, the Vandals won the first of three consecutive, their only three-peat in the rivalry series.

The Boise game against Wyoming on the third anniversary of Armistice Day was attended by Governor D. W. Davis.

The following June, Kelley left for the University of Missouri. and was succeeded at Idaho in 1922 by Robert "Matty" Mathews.