Borknagar was founded by a remaining member of the Norwegian death metal band Molested when then-member Øystein Brun became tired of the brutal aspects of the band's music. Øystein formed Borknagar to explore a more melodic outlet of expression, inspired by the burgeoning black metal movement Norway was experiencing and looking to push the boundaries of what was considered "traditional" black metal music. He wrote all of the music and lyrics, and gathered together an all-star group of black metal musicians to play in his band, such as Infernus of Gorgoroth, Grim of Immortal and Gorgoroth, and Ivar Bjørnson of Enslaved. When Garm of Ulver, Head Control System, and Arcturus joined the project, it brought the band immediate attention. The band never even recorded a demo; they simply asked for a record contract on Malicious Records and were granted their request based on the strength of this lineup. Borknagar's music instantly gained fans and received positive press attention.

Borknagar has released ten albums to date. Their self-titled debut album features lyrics solely in Norwegian; all subsequent albums have featured lyrics written in English exclusively (however, The Olden Domain featured an instrumental track titled in Norwegian). Aside from Brun's lyrical contributions, the band has featured lyrics by other members as well: ICS Vortex from Arcturus and ex-Dimmu Borgir, drummer Asgeir Mickelson, keyboardist Lars Nedland and more recently by current singer Vintersorg from Otyg and his eponymous band. Bassist Jan Erik Tiwaz (a.k.a. Tyr) wrote the song 'The View of Everlast'. All of the band's records (excluding the original pressing of the debut album) have been released by the label Century Media. Borknagar has toured with various bands including Emperor, Peccatum, In Flames, Morbid Angel, and Cradle of Filth.