John Thomas O'Sullivan is an American former professional football quarterback who played nine seasons in the National Football League (NFL), two seasons in NFL Europe and one season in the Canadian Football League (CFL). He played college football for the UC Davis Aggies, starting for three years and throwing 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.

The UC Davis Aggies football team represents the University of California, Davis in NCAA Division I Football Championship Subdivision (FCS). The football program's first season took place in 1915, and has fielded a team each year since with the exception of 1918 during World War I and from 1943 to 1945 during World War II, when the campus, then known as the University Farm, was shut down. The team was known as the Cal Aggies or California Aggies from 1922 to 1958 when UC Davis was called the Northern Branch of the College of Agriculture.