Illinois Route 31 (IL 31) is a 58.41-mile-long (94.00 km) north–south state highway in northeastern Illinois, United States. It travels from U.S. Route 34 (US 34) in Oswego north to US 12, near the Wisconsin state line, just south of Richmond.

U.S. Route 34 (US 34) is an east–west highway In the state of Illinois that runs from the Iowa state line at Gulfport, west of Galesburg, to Illinois Route 43 (IL 43) and Historic U.S. Route 66 at Harlem Avenue in Berwyn. The entire highway in Illinois is named the Walter Payton Memorial Highway after Pro Football Hall of Famer Walter Payton, who wore #34 for the Chicago Bears. The highway is 211.37 miles (340.17 km) long within the state.