Illinois Route 124 (IL 124) is a 5.71-mile-long (9.19 km) state route in central Illinois.

IL 124 runs from IL 123 between Athens and Williamsville to the Business Loop for Interstate 55 (I-55) around Springfield at Sherman.

[1] Illinois 124 is a rural, two-lane surface street for its entire length.

In 1940 the route was changed to Illinois 29, and former Illinois Route 24 was changed to Illinois Route 124, running east from Athens to the current northern terminus, and south to the Business Loop.

[2] The entire route is in Sangamon County.