The Illinois River is a large tributary of the Mississippi River in the U.S. state of Illinois.
Illinois River may refer to:
- Illinois River (Arkansas–Oklahoma), a tributary of the Arkansas River, in Arkansas and Oklahoma in the United States
- Illinois River (Oregon), a tributary of the Rogue River, in Oregon in the United States
- Illinois River (Colorado) a tributary of the Michigan River, in Jackson County, Colorado in the United States
See also
- Illinois (disambiguation)
- Illinois River Bridge (disambiguation)
- List of rivers of Illinois <!-- can be referred to as "Illinois river(s)" -->