The 1990–91 UNLV Runnin' Rebels basketball team represented the University of Nevada, Las Vegas in NCAA Division I men's competition in the 1990–91 season.

The Runnin' Rebels, coached by Jerry Tarkanian, entered the season as defending national champions and entered the 1991 NCAA tournament unbeaten, but lost in the national semifinal to eventual champions Duke when Anderson Hunt's desperation three in the final seconds bounced off the backboard and into the hands of a Duke player, Bobby Hurley, ending a 45-game winning streak that dated back to the previous season.

They were the last team to enter the NCAA tournament unbeaten until Wichita State did it in 2014, Kentucky in 2015, and Gonzaga in 2021.

The team played its home games in the Thomas & Mack Center, and was a member of the Big West Conference.

UNLV’s semi-final loss in the NCAA tournament brought an end to their astounding 45-game win streak.