The following is a list of Illinois High School Association member conferences. Schools that belong to these conferences compete with each other on a local level in athletics and non-athletic activities. As of the 2023-24 school year, there are 70 conferences within the IHSA.

• Apollo Conference
• Big Northern Conference
• Big Twelve Conference
• Black Diamond Conference
• Cahokia Conference (contains three divisions)
• Central Illinois Conference
• Central State Eight Conference
• Central Suburban League (contains two divisions)
• Chicago Catholic League (contains two divisions)
• Chicago Prep Conference
• Chicago Public High School League (contains ten divisions)
• Chicagoland Christian Conference
• DuKane Conference
• DuPage Valley Conference
• East Central Illinois Conference
• East Suburban Catholic Conference
• Egyptian Illini Conference
• Fox Valley Conference
• Gateway Metro Conference
• Girls Catholic Athletic Conference
• Greater Egyptian Conference
• Heart of Illinois Conference
• Illini Prairie Conference
• Illinois Central Eight Conference
• Independent School League
• Inter County Athletic Conference
• Interstate Eight Conference
• Kishwaukee River Conference
• Lake Shore Athletic Conference
• Lincoln Prairie Conference
• Lincoln Trail Conference
• Little Illini Conference
• Little Okaw Valley Conference
• Little Ten Conference
• Metro Suburban Conference
• Metropolitan Prep Conference
• Mid-Illini Conference
• Midland Trail Conference
• Mid-Suburban League (contains two divisions)
• Mississippi Valley Conference
• MSM Conference
• National Trail Conference
• Noble Athletic Conference
• North Suburban Conference
• Northeastern Athletic Conference
• Northern Illinois Conference (NIC-10)
• Northern Lake County Conference
• Northwest Upstate Illini Conference (contains two divisions)
• Pike County Conference
• Prairieland Conference
• River Valley Conference
• Sangamo Conference
• South Central Conference (Illinois)
• South Egyptian Conference
• South Seven Conference
• South Suburban Conference
• Southern Illinois River-to-River Conference (with Mississippi and Ohio River divisions)
• Southland Athletic Conference
• Southwest Prairie Conference
• Southwest Suburban Conference
• Southwestern Conference
• Three Rivers Conference
• Tomahawk Conference (Illinois)
• Tri-County Conference
• Upstate Eight Conference
• Vermilion Valley Conference
• West Central Conference
• West Suburban Conference (contains two divisions)
• Western Big 6 Conference
• Western Illinois Valley Conference (contains two divisions)

• Ambraw Valley Conference (1945-1955)
• Big 8 (1980-1995)
• Big Rivers Conference (football-only) (1999-2012)
• Bi-County Conference (1917-1919)
• Bi-County Conference (1970s-1998)
• Blackhawk Conference (West) (1934-1990)
• Blackhawk Conference (North) (1947-1972)
• Bureau Valley Conference (1970s-1990s)
• Capitol Conference (1964-1982)
• Cenois Conference (1963-1969)
• Central Conference (1956-1958)
• Central Egyptian Conference (1929-1940)
• Chicagoland Prep Conference (1961-1969)
• Coal Belt Conference (1946-1956)
• Cook County High School League (1889–1913)
• Corn Belt Conference (1950–2017)
• Des Plaines Valley Conference (1963-1985)
• East Okaw Conference (1981-1995)
• Eastern Illinois Conference (1952-1969)
• Four Rivers Conference (2000-2006)
• Fox Valley Conference (1952-1966)
• Gateway East Conference (1979-1983)
• Greater Midwestern Conference (1983-1986)
• Heartland Conference (Illinois) (1978-1982)
• Heart of Illinois Conference (1970s) (1972–1978)
• Illini Central Conference (1985-1998)
• Illini 8 Conference (1966-1981)
• Illini Valley Conference (North Central) (1970-1972)
• Illini Valley Conference (South Central) (1928-1973)
• Illio Conference (1952-1975)
• Illowa Conference (1952-1974)
• Indian Valley Conference (1976-1994)
• Iroquois Conference (1970s-1980s)
• Kane County Conference (????-1917)
• Kankakee Valley Conference (1950-1979)
• La Moine Valley Conference (1952-1967)
• Little 6 Conference (1952–1975)
• Little 7 Conference (1921–1995)
• Little 8 Conference (North Central) (1921–1975)
• Little 8 Conference (Far North) (1920s–1980)
• Little 8 Conference (Northeast) (1919–19??)
• Little 8 Conference (Northwest) (1918–192?)
• Little 8 Conference (Southwest) (????–????)
• Little Egypt Conference (1960s-1970s)
• Little Five Conference (1923-1939)
• Little Four Conference (19??'s-1948)
• Meridian Conference (Central Illinois) (1959-1993)
• Meridian Conference (Northern Illinois) (????-????)
• Metro Catholic Conference (1960-1965)
• Mid Northern Confernce (1972-1995)
• Mid-South Conference (1983-2008)
• Mid-State Conference (1944-1997)
• Mid-State Six Conference (196?-2015)
• Midwest Conference (1948-1970)
• Midwestern Conference (1952-1970)
• Mississippi Valley Conference (1957-1968)
• New Salem Conference
• North Central Illinois Conference (1929-2011)
• North Egypt Conference (1938-2003)
• North Shore Conference (1904-1914)
• North Six Conference (1939-1946)
• Northern Illinois Big 12 Conference (2010-2018)
• Northwest Conference (1963-1974)
• Northwest Illinois Conference (NWIC) (1974-1996)
• Northwest 7 Conference (1972-1973)
• Northwest 8 Conference (1977-1990)
• Northwest Suburban Conference (1925-1997)
• Okaw Valley Conference (1950s-2017)
• Olympic Conference (1976-2010)
• PMSC Conference (1961-1973)
• Prairie State Conference (1985-????)
• Quad Cities Metro Conference (1950-1977)
• River Trails Conference (1990-1995)
• Rock River (Valley) Conference (1924-1948)
• Route 72 Conference (1952-1972)
• Sangamon Valley Conference (1948-2021)
• SHARK Conference (1946-1982)
• SICA — (South Inter-Conference Association, dissolved 2006)
• Southeast Suburban Conference (1962-1972)
• Southern Conference (IHSA) (????-????)
• Southern Illini Conference (1957-1974)
• Southern Illini Conference (1986-1993)
• Southwest Egyptian Conference (????-1993)
• Spoon River Conference (1959-1985)
• Stephenson County Conference (1958-1963) (Renamed "Northwest Illinois Conference")
• Suburban Catholic Conference (1960-1973)
• Suburban Catholic Conference (2009-2015)
• Suburban League (1913–1975)
• Suburban Prairie Conference (1995-2005)
• SWANI Conference (1946-1953)
• Tollway Athletic Conference
• Trailblazer Conference (1982-1984)
• Tri State Conference (1932-1935)
• Two Rivers Conference (19??-1958)
• United Conference (1958-1963)
• Upstate Illini Conference (1974-1976)
• Upstate Illini Conference (1991-2000)
• US Grant Conference (1950-1958)
• Vermilion Valley Conference (1950-1981)
• Wauseca Conference (1928-1989)
• West Prairie Trail Conference
• Western Area Conference (1974-1996)
• Western Athletic Conference (1908-1921)
• Western Sun Conference (2006-2010)
• Western Suburban Athletic Conference (1903-1910)
• Western Suburban Catholic Conference (1974-1988)
• Wilco Conference (1959-1973)
• Wil-Ro-Kee Conference (1954-1959) (Renamed "Kankakee Valley Conference" in 1960)

• Illinois High School Association, Official Site
• IHSA Conferences and Leagues