Ordo Ad Chao is the fourth full-length album by the Norwegian black metal band Mayhem. The album received the Spellemann Award for best heavy metal album on 2 February 2008.

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 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 of Burzum.