Big Twelve Conference (Illinois)

The Big Twelve Conference is a high school athletic conference in the Illinois High School Association (IHSA), based in Central Illinois. While the name implies that the conference has twelve schools, there are actually only eleven schools currently active, due to other schools either closing, ending offering varsity athletics, or changing conferences.

The conference was indirectly responsible for the demise of the Capitol Conference in 1983 after voting to remove Springfield High School and add four schools from that conference.

All of the schools in the conference are located in cities on Interstate 74 which runs through central Illinois.