Jonas Kjellgren is a Swedish musician and producer, now residing in Grangärde. He has been lead vocalist for Carnal Forge and Dellamorte, played guitar for Centinex, and played bass for October Tide. He is most famous for being the former co-founder and guitarist of Scar Symmetry, founded in 2005. As a producer, he has worked with bands such as Sonic Syndicate, Zonaria, Steel Attack, 21Lucifers, Darzamat and The Absence. He owns and operates Black Lounge Studios, which many Swedish metal bands use to record, mix and master their albums, although most of his own production efforts are done at The Abyss, which is owned by Peter Tägtgren. Kjellgren is known for playing seven-string guitars.

Carnal Forge are a Swedish band, best classified as thrash metal with some melodic death metal influences. Their name originates from a song on Carcass's album Heartwork.