Illinois Route 117 is a rural north–south state route in north central Illinois. It travels from Interstate 74 in the small community of Goodfield to Illinois Route 17 in Toluca. Illinois 117 covers a distance of about .
|location=Benson–Toluca, Illinois
|established=1929
|decommissioned=January 1993
Though Illinois 117 now connects to Illinois 17, they were originally unconnected, and each were separately planned in State Bond Issue sequence. SBI Route 117 originally ran from U.S. Route 150 (just north of current I-74) in Goodfield to Illinois 116 north of Eureka. On January 8, 1993, it was extended north through Roanoke and north to Toluca to renumber IL 116A, the last surviving letter route in Illinois.