Lock Up the Wolves is the fifth studio album by American heavy metal band Dio, released on May 15, 1990, through Reprise Records in North America, and through Vertigo Records elsewhere. The album displayed a complete line-up change over the previous album, Dream Evil, including then 18-year-old guitarist Rowan Robertson, former AC/DC drummer Simon Wright, keyboardist Jens Johansson, and bassist Teddy Cook, who was in the band Hotshot, which morphed into Danger Danger. Rod Simpkins, from Riken and Jungle Alley, would replace Cook as bassist for several tour dates in 1990.