Jay Dee "B.J." Penn (born December 13, 1978 in Hilo, Hawaii) is an American mixed martial artist. He fights for the UFC. Penn is a former one-time UFC Lightweight Champion and one-time UFC Welterweight Champion. Penn was also the coach of the 5th season of The Ultimate Fighter against the other coach, Jens Pulver. Penn is also a former one-time "Rumble on the Rock" Lightweight Champion.