Illinois Route 113 is a two-lane state road that runs east from Illinois Route 47 north of Mazon and east of Seneca to Illinois Route 17 in western Kankakee, just across the Kankakee River from U.S. Route 45 and U.S. Route 52. This is a distance of 34.11 miles (54.89 km).

Illinois 113 is the southern parallel of Illinois Route 102, which parallels the Kankakee River on the northern side.

SBI Route 113 was the name of both roads on the north and south sides of the Kankakee River from Diamond (between Coal City and Braidwood on Interstate 55) to Kankakee. In 1940, the route became Illinois Route 113N and Illinois Route 113S, with 113N as the northern route and 113S as the southern, with 113S used as the western end to U.S. Route 66 (now Interstate 55). In 1961, Illinois 113S became Illinois Route 113, and 113N was renamed Illinois Route 102.