Chemung, elevation 896 feet (273 meters), is an unincorporated census-designated place in McHenry County, Illinois, United States.

[3] A post office called Chemung was established in 1845, and remained in operation until it was discontinued in 1943.

[5] The small, unincorporated town is located approximately 3.14 miles west of downtown Harvard, Illinois at the junction of Illinois Route 173, Oak Grove Road (County Highway A-20) and Island Road (the continuation of Oak Grove Road south of Route 173).

In terms of geographic coordinates, Chemung is located at 42°24′55″N 88°40′00″W / 42.41528°N 88.66667°W / 42.41528; -88.66667 (42.4152964, -88.6667668) [6] In terms of the Public Land Survey System, Chemung is found in Sections 4 and 5, Township 45 North, Range 5 East; and Sections 32 and 33, Township 46 North, Range 5 East of the Third Principal Meridian.

Piscasaw Creek flows along the west side of Chemung in a generally northeast to southwest direction,[7] and a freight branch line of the Union Pacific Railroad traverses the town in an east-northeast to west-southwest direction.