John Thomas O'Sullivan (born August 25, 1979) is an American former professional gridiron football quarterback and the former head football coach of Patrick Henry High School (San Diego, California) who played in the National Football League (NFL), NFL Europe and Canadian Football League (CFL) from 2002 to 2012. He played college football for the UC Davis Aggies of the University of California, Davis, where he was a three-year starter and threw for career totals of 10,745 yards and 96 touchdowns. He was named a First-team All-American in 2000 and a Second-team All-American in 2001. He was inducted into the Cal Aggie Athletics Hall of Fame in 2008.