Illinois Route 157 is a north–south highway in southwestern Illinois. Its southern terminus is at Illinois Route 3 at Cahokia, Illinois and its northern terminus at Illinois Route 140 in Hamel. This is a distance of 35.50 miles (57.13 km).

Illinois 157 overlaps Illinois Route 13 and Illinois Route 163 in Centreville and Illinois Route 159 and Illinois Route 143 in Edwardsville. Illinois 157 is the major north–south road through the busiest towns in Madison County — Collinsville and Edwardsville.

The segment of road within the villages of Cahokia and Centreville from Illinois 3 to Illinois 13 is known as Camp Jackson Road.

The segment of road north from Illinois 13 to approximately Interstate 270 is known as Bluff Road, because it roughly follows the eastern bluffs of the Mississippi River which define the American Bottoms in Madison and St. Clair Counties of Illinois.

SBI Route 157 originally ran from Cahokia to Glen Carbon. It was then extended to the Missouri state line at the Jefferson Barracks Bridge in 1946; this was undone by 1958. In 1965, the northern terminus was moved to Hamel, replacing Bypass U.S. Route 66, which itself was U.S. 66 proper prior to 1957.