Mayhem is a Norwegian black metal band formed in Oslo in 1984. They were one of the pioneers of the Norwegian black metal scene, and their music has profoundly influenced the black metal genre. Mayhem's early career was marked by controversy, primarily due to their notorious live performances, the 1991 suicide of vocalist Per Yngve Ohlin ("Dead"), and the 1993 murder of guitarist Øystein Aarseth ("Euronymous") by former member Varg Vikernes ("Count Grishnackh") of Burzum.

The group released a demo and an EP that were highly influential, amassing a devoted following through sporadic and notorious live performances while attracting further attention due to their connections with the series of Norwegian church burnings and the incidents of violence surrounding them. Mayhem temporarily disbanded following Aarseth's murder, shortly before the release of their debut album, De Mysteriis Dom Sathanas, which is regarded as a classic of the black metal genre. Surviving former members Jan Axel Blomberg ("Hellhammer"), Jørn Stubberud ("Necrobutcher"), and Sven Erik Kristiansen ("Maniac") reformed the band in 1995, with Rune Eriksen ("Blasphemer") replacing Aarseth. Attila Csihar and Morten Iversen ("Teloch") have since replaced Kristiansen and Eriksen, respectively. Their post-Aarseth material is characterized by increased experimentation. The 2007 album Ordo Ad Chao received the Spellemann Award for Best Heavy Metal Album.