U.D.O is a German heavy metal band formed by Udo Dirkschneider. He formed the band in 1987 following his first departure from the band Accept. Udo recruited four more members and released their debut album Animal House. The album was completely written by Accept.

The band would release three more albums until Dirkschnieder put the band on hiatus to reunite with accept. Dirkschnieder reactivated U.D.O with almost a completely new line up in 1992. Since then the band has continued to release albums through various line-up changes.