Ace Tomas "Quorthon" Forsberg (1966 – 2004) was the founder and song writer of the pioneering Swedish black metal band Bathory. His fans considered him the "father" of both the black metal and viking metal genres, the latter having a more evolved and operatic style.

Quorthon formed Bathory in 1984 when he was 18 years old. Always underfunded, the quality of the albums was rough and eventually created a style that many bands would later emulate. In fact, he personally paid for the production of Bathory's music video for "One Road to Asa Bay" in 1990. The video was shown on MTV's Headbanger's Ball, though he had not yet seen it at the time he was interviewed for the program.

Beginning in the 1990s, he took full control of Bathory, choosing to forego performing live in order to spend time recording music with hired musicians. He was found dead in his apartment on June 7, 2004, apparently from heart failure. He was 39 years old and was known to suffer from heart problems.

His father, Börje "Boss" Forsberg, is the owner of Black Mark Productions, an independent record label that Quorthon founded.