NCAA Division I men's basketball tournament upsets

An upset is a victory by an underdog team. In the context of the NCAA Division I men's basketball tournament, a single-elimination tournament, this generally constitutes a team defeating an opponent with a substantially higher seed. The NCAA defines a tournament upset as a victory by a team seeded five or more lines below the opponent that it defeats.

This is the list of victories by teams seeded 11 or lower in the First and Second Rounds of the tournament, as well as those by teams seeded 8 or 9 against 1 and 7 or 10 against 2 seeds in the Second Round, since it expanded to 64 teams in 1985. Because these low-seeded teams are automatically paired against higher-seeded teams at the start of the tournament, they are almost always underdogs, and their victories are almost always considered upsets. The list also includes victories by teams seeded 8 or lower in the Sweet Sixteen (the four regional semifinals), teams seeded 7 or lower in the Elite Eight (the four regional finals), and teams seeded 6 or lower in the Final Four. All teams are listed by athletic brand names they used at the time of their wins, which do not always match those in use today.