Jason Mizell (born January 21, 1965, Brooklyn, New York, USA – died October 30, 2002, Queens, New York, USA) was an American musician and DJ known as Jam Master Jay. At the age of 3 years he started playing trumpet and played bass, guitar, and drums in various bands prior to discovering turntables. He moved to Hollis, Queens in 1975 with his family where he soon discovered the turntables and started DJ-ing at the age of 13.

In 1982, he hooked up with Joseph Simmons and Darryl McDaniels of Run-DMC just after they graduated from high school and agreed to DJ for them because he wanted to be part of the band. On Run-D.M.C's album Raising Hell, Mizell played keyboards, bass, and live drums in addition to his turntable work

On October 30, 2002, at 7:30 pm Mizell was shot and killed in a Merrick Boulevard recording studio in Jamaica, Queens.