Sullivan High School is a public high school in Sullivan, Illinois, which is in central Illinois, near Decatur. It currently competes as a member of the Okaw Valley Conference. It also competes in Class A, the "small school" division, of the Illinois High School Association's (IHSA) State Championship Series.
The team was a small school power for many years under the leadership of Ken Johnson, finishing 4th in the IHSA Class A Tournament in 1993. Johnson is a Member of the IHSSBCA Hall of Fame. The school also finished 4th in the IHSA Tournament in 2001, when it was coached by Toby Bolsen.