Mayhem is a Norwegian black metal band formed in Langhus in 1984. They were one of the founders of the Norwegian black metal scene, and their music has strongly influenced the black metal genre. Mayhem's early career was highly controversial, primarily because of 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, and amassed a loyal following through sporadic and notorious live performances, attracting further attention through their ties to the string of Norwegian church burnings and the incidents of violence surrounding them. Mayhem temporarily disbanded after Aarseth's murder, shortly before the release of their debut album, De Mysteriis Dom Sathanas, 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.