The 2021 NCAA Division I men's basketball tournament was a single-elimination tournament of 68 teams to determine the National Collegiate Athletic Association (NCAA) Division I men's college basketball national champion for the 2020–21 season. The 82nd edition of the tournament began play on March 18, 2021 in sites around the state of Indiana, and concluded with the championship game at Lucas Oil Stadium in Indianapolis on April 5, with the Baylor Bears defeating the previously undefeated Gonzaga Bulldogs 86–70 to earn the team's first ever title.

The NCAA Division I men's basketball tournament, branded as March Madness, is a single-elimination tournament played in the United States to determine the men's college basketball national champion of the Division I level in the National Collegiate Athletic Association. Played mostly during March, the tournament consists of 68 teams and was first conducted in 1939. Known for its upsets of favored teams, it has become one of the biggest annual sporting events in the US.