Celtic Frost (/ˈkɛltɪk frɒst/) was a Swiss extreme metal band from Zürich. They are known for their heavy influence on the extreme metal genres. Formed in 1981 as Hellhammer, the band became Celtic Frost in 1984 and was active until 1993. It re-formed in 2001 and disbanded following frontman Tom Gabriel Fischer's departure in 2008. The band was inspired by heavy metal groups such as Black Sabbath, Judas Priest and Venom, but also by gothic rock acts like Bauhaus, Siouxsie and the Banshees and Christian Death, and by the hardcore punk group Discharge.

Their music included elements of various extreme metal styles. Their earlier music was sometimes classified as thrash metal, black metal and death metal and their later work as doom metal and gothic metal. The level of experimentation on albums such as Into the Pandemonium led certain journalists to describe the band's direction as avant-garde metal.