March Madness is an annual college basketball tournament held in the United States, featuring 68 teams from the National Collegiate Athletic Association (NCAA). The tournament typically begins in mid-March and culminates in early April, showcasing a single-elimination format where teams compete to advance through various rounds until a national champion is crowned. The event is known for its excitement and unpredictability, often leading to surprising upsets and thrilling games. Fans engage in filling out brackets, predicting outcomes for each matchup, which adds to the tournament's popularity and cultural significance in American sports.