Illinois Route 90 is an east–west state highway in northern Peoria County in central Illinois. It runs from Illinois Route 78 in Laura to Illinois Route 40 in Edelstein. This is a distance of 15.80 miles (25.43 km).

Illinois 90 is a rural, undivided two-lane surface road for its entire length. It crosses the towns of Monica and Princeville, overlapping Illinois Route 91 from Princeville east for 4 miles (7 km).

SBI Route 90 ran from Laura in Peoria County to Sparland in Marshall County along current Illinois 90, Illinois Route 17 and Illinois Route 40. This was changed to its current alignment in 1938.