March Madness is a popular colloquial term for the process of deciding the annual champion of NCAA collegiate basketball in the United States. The tournament takes place during the months of March and April, and the term refers to the frenzy it ignites among the sports fans and gamblers. The term is used in reference to both the men's and women's tournaments.

Initially, the champions of each Division I conference are given automatic bids, and the remaining slots are filled by at-large berths, selected by the NCAA Selection Committee. The at-large selection process and the seedings for each team depend on several factors, including the teams' respective ranking, record, RPI, and the difficulty of opponents played.

The men's tournament consists of 65 teams, with the two lowest-rated teams playing an Opening Round game to determine who advances into the First Round of the tournament. This play-in game was added in 2001 in order to allow one more at-large team into the tournament, and has been played in Dayton, Ohio since its creation. The women's tournament consists of 64 teams and does not have a play-in game between the two lowest-rated teams.

See NCAA Men's Division I Basketball Championship and NCAA Women's Division I Basketball Championship for details.

See also

• Selection Sunday
• Final Four
• Bracketology