Kingdom of Sorrow is an American sludge metal band that features Kirk Windstein of Crowbar and Down, along with Jamey Jasta of Hatebreed.

Kirk Windstein is an American musician. He is the frontman, vocalist, rhythm guitarist, and sole constant member of the sludge metal band Crowbar. He is also a founding member of the heavy metal supergroup Down, playing guitar with them from 1991 to 2013 and later rejoining the band in 2020. In 2005, Windstein formed Kingdom of Sorrow with Jamey Jasta of Hatebreed. Their debut album was released in 2008. Windstein began his musical career in 1985 as a guitarist for a cover band called Victorian Blitz, and in 1988 joined a hardcore punk band called Shell Shock as a vocalist and guitarist.