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