Kjetil Tvedte Grutle, better known as Grutle Kjellson, is a Norwegian musician, best known as the bassist and vocalist of the extreme metal band Enslaved. Kjellson and guitarist Ivar Bjørnson are the founding and only constant members of the band, as well as the main songwriters. He has released sixteen studio albums with Enslaved and won five Norwegian Spellemann Awards with the band.