Def Jef is the stage name of Jeffrey Fortson (born 27 September 1966), an American alternative hip hop musician and rapper of the late 1980s and early 1990s. He was born in Harlem, New York City, New York, USA.

His debut album was 1989's Just a Poet With a Soul, which won critical acclaim for sociopolitical lyrics and original beats. Additionally, he was a member of the West Coast Rap All-Stars, a collaboration of West Coast-based hip hop artists who released the anti-violence single "We're All in the Same Gang" in 1990. He performed on the television variety show In Living Color in 1990.