Billboard.com said the guitarist died Thursday while on tour in Pennsylvania. The cause of his death was not reported.
"Magic Slim embodied the heart and soul of this label," Blind Pig Records owner Jerry Del Giudice told Billboard.com. "It was Magic Slim, and the guys like him, and their music, that inspired us to start the label in the first place."
Holt signed with Blind Pig in 1990 and the label released 10 of his albums through 2012.
The musician and his band the Teardrops won numerous Blues Music Awards and the state of Mississippi erected in 2011 a Blues Trail Marker in front of a building in Grenada where Holt's mother had operated a restaurant.
Holt and the Teardrops, who played for years in Chicago's nightclubs, have been described as "the last real Chicago blues band," Billboard.com said.