The Chemung River is a tributary of the Susquehanna River, approximately 46.4 miles (74.7 km) 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 Chemung River is formed near Painted Post in Steuben County, just west of Corning by the confluence of the Tioga River and Cohocton rivers. It flows generally east-southeast through Corning, Big Flats, Elmira, and Waverly. It crosses into northern Pennsylvania before joining the Susquehanna River approximately 2 miles (3 km) south of Sayre.