The Chemung River is a tributary of the Susquehanna River, approximately 46.4 miles long, in south central New York and northern Pennsylvania in the United States. It drains a mountainous region of the northern Allegheny Plateau in the Southern Tier of New York. The valley of the river has long been an important manufacturing center in the region but has suffered a decline in the late 20th century.
The area near the river's source was referred to as Concanoga, or the land of three rivers, by the Seneca who lived in the area. In colonial times the river valley was a major trade route through the hill country of western New York, first for the Iroquois and other Native Americans, and later for the European settlers.
In 1779 during the Revolutionary War, American troops of the Sullivan Expedition defeated a combined force of Iroquois, Tories and British at the Battle of Newtown along the river southeast of Elmira. The victory opened the way for Sullivan to systematically destroy Iroquois villages and settlements throughout their homeland of central and western New York.