Illinois 203 (disambiguation)

Illinois 203 could refer to:
 * Illinois Route 203, a state highway, formerly part of Illinois Route 3 and U.S. Route 66, near St. Louis


 * School districts
 * Elwood Community Consolidated School District 203 in Will County
 * Naperville Community Unit School District 203 in DuPage County
 * New Trier Township High School District 203 in Cook County
 * O'Fallon Township High School District 203 in St. Clair County
 * Orangeville Community Unit School District 203 in Stephenson County
 * Vandalia Community Unit School District 203 in Fayette County
 * Westmer Community Unit School District 203 in Mercer County