The Amateur Athletic Union, widely known as the AAU, was formed in 1888 to sponsor US teams and players in a wide variety of sports, and has sponsored many tournaments throughout the United States. Its goal is to help athletes get noticed, to direct them toward a good college or into the right environment in their community. The summit AAU events are the annual AAU Junior Olympic Games. Until the 1970s it was the recognized governing body for many prominent sports in the United States, such as swimming and track and field, but it gave up its jurisdiction with the decline of amateurism.

The AAU has engaged in a long-running feud with the National Collegiate Athletic Association over control of amateur athletics, especially track and field and the status of sportswomen. Early in the twentieth century the AAU developed a strong link with the American Olympic Committee because of its influence in track and field, swimming, and gymnastics. By the 1930s, however, it had conceded control over Olympic qualifications to the NCAA in a number of sports.

Until the Amateur Sports Act of 1978, the AAU had complete control over athletes' amateur status, meaning they decided if an athlete was eligible to compete in the Olympics. Outspoken track star Steve Prefontaine began to protest the living conditions for amateur athletes under the AAU where many of the best American athletes were forced to live on food stamps. Other controversies with the AAU include its restrictions on track star Wes Santee that may have stopped him from breaking the 4 minute barrier.

Each year, the AAU awards the James E. Sullivan Award to the top amateur athlete in the United States.