The Amateur Athletic Union AAU Beach Volleyball Santa Monica Volleyball Tournament on Saturday, June 6, 2015. The Amateur Athletic Union (AAU) is one of the largest amateur multi-sports organizations in the USA. The AAU was founded in 1888 to establish standards and uniformity in amateur sport. During its early years the AAU served as a leader in international sport representing the United States in the international sports federations. The AAU worked closely with the Olympic movement to prepare athletes for the Olympic Games.