The early rounds of the one-and-done competition of loaded with them. From No. 15 seeds topping No. 2s to those schools that make a surprise run into the Sweet Sixteen as a result of a buzzer-beater, the Big Dance has traditionally featured these bracket-busting outcomes.
Although there have been many upsets in the tournament's history, here are five games that stand among some of the biggest shockers:
1991: Richmond vs. Syracuse
Richmond added its name to the list of all time shockers after ousting Syracuse 73-69, becoming the first No. 15 seed to defeat a No. 2 at the tournament.
1996: Princeton vs. UCLA
Princeton, a 13 seed, stunned No. 4 UCLA (the defending NCAA champs at the time) 43-41 in an opening round game that remains one of the biggest wins in Tigers history.
2001: Hampton vs. Iowa State
The Pirates, a 15 seed, made No. 2 Iowa State walk the blank in a 58-57 squeaker that sent Hampton players and fans into a frenzy.
2006: George Mason vs. UConn
Overtime was needed for George Mason to down Connecticut, a team favored to win the title, 86-84 in an Elite Eight match-up that had all the makings of an upset from the start. George Mason, the tournament's Cinderella team that year, went on to reach the Final Four, losing to eventual champion Florida.
2012: Norfolk State vs. Missouri
In yet another No. 15 seed knocking off a No. 2, Norfolk State bounced Missouri from the tournament -- the first time since that 2001 Hampton upset -- that may have been one of the biggest bracket-busters in tourney history. Only two of the 6.45 million participants in ESPN.com's bracket challenge still had perfect records -- mainly because of Norfolk State's 86-84 victory. Even President Obama had Missouri going to the Final Four that year.