1990–91 Idaho Vandals men's basketball team

The 1990–91 Idaho Vandals men's basketball team represented the University of Idaho during the 1990–91 NCAA Division I men's basketball season. Members of the Big Sky Conference, the Vandals were led by first-year head coach Larry Eustachy and played their home games on campus at the Kibbie Dome in Moscow, Idaho.

The Vandals were 17–10 overall in the regular season and 11–5 in conference play, third place in the league standings.

At the conference tournament in Missoula, the Vandals defeated second-seed Nevada by nineteen points in the semifinals and were on the verge of a third consecutive title, but lost by eight points in the final to host Montana.

Postseason results
!colspan=6 style=| Big Sky tournament