The 2008–09 United States Open Cup for Arena Soccer was the first open knockout style tournament for Arena/Indoor Soccer.
In its inaugural season, the St. Louis Illusion were cup winners, due to their victory over the Detroit Waza and the Stockton Cougars inability to field a team for the final due to the late finish of the competition.
† Due to the withdrawal of the Semifinal Winning Stockton Cougars before April 18, what was originally supposed to be a Semifinal Match between the St. Louis Illusion and Detroit Waza became the Championship Match.
[1] San Diego Fusion qualify for US Arena Open Cup Round of 16 Final: November 22, 2008 OTW Santa Clara 7, Turlock Express 2 OTW Santa Clara qualify for US Arena Open Cup Round of 16