The NCAA Division I Men's Basketball Tournament (known informally as March Madness or the Big Dance) is a single-elimination tournament played each spring in the United States, currently featuring 68 college basketball teams from the Division I level of the National Collegiate Athletic Association (NCAA), to determine the national championship. The tournament was created in 1939 by the National Association of Basketball Coaches, and was the idea of Ohio State University coach Harold Olsen. Played mostly during March, it has become one of the most famous annual sporting events in the United States.
The tournament teams include champions from 32 Division I conferences (which receive automatic bids), and 36 teams which are awarded at-large berths. These "at-large" teams are chosen by an NCAA selection committee, then announced in a nationally televised event on the Sunday preceding the "First Four" play-in games, currently held in Dayton, Ohio, and dubbed Selection Sunday. The 68 teams are divided into four regions and organized into a single-elimination "bracket", which pre-determines, when a team wins a game, which team it will face next. Each team is "seeded", or ranked, within its region from 1 to 16. After the First Four, the tournament occurs during the course of three weekends, at pre-selected neutral sites across the United States.
Teams, seeded by rank, proceed through a single-game elimination bracket beginning with a "first four" consisting of 8 low-seeded teams playing in 4 games for a position in the first round the Tuesday and Wednesday before the first round begins, a first round consisting of 64 teams playing in 32 games over the course of a week, the "Sweet Sixteen" and "Elite Eight" rounds the next week and weekend, respectively, and – for the last weekend of the tournament – the "Final Four" round. The Final Four is usually played during the first weekend of April. These four teams, one from each region (East, South, Midwest, and West), compete in a preselected location for the national championship.
The tournament has been at least partially televised since 1969. Currently, the games are broadcast by CBS, TBS, TNT, and truTV under the trade-name NCAA March Madness. Since 2011, all games are available for viewing nationwide and internationally, such as in the Philippines and Canada. As television coverage has grown, so too has the tournament's popularity. Currently, millions of Americans fill out a bracket, attempting to correctly predict the outcome of all 67 games of the tournament.