Antonio "L.A." Reid will leave his job as chairman of Island Def Jam to become a judge on Simon Cowell's upcoming show "The X Factor," a source familiar with Cowell's offer confirmed to Billboard Wednesday.
Reid accepted an offer from Cowell this week to join the Fox television show, which will begin airing in September, the source said. Reid's contract was due to expire in December.
Island Def Jam will continue to be run by Steve Bartels. Barry Weiss, the former Sony Music executive joining Universal Music Group this month , is expected to add oversight of Island Def Jam to his duties.
The question remains, however, whether Reid will eventually join his former Universal boss Doug Morris, who becomes CEO of Sony Music on July 1. 
Sony Music has vested interest in the competition: Recordings of the show's contestants will be controlled by Simon Cowell's Syco and Sony Music and the winner will receive a $5 million contract with Sony Music.
Auditions begin March 27 in Los Angeles.