The Chemung River (/ʃəˈmʌŋ/ shə-MUNG) 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 valley of the river has long been an important manufacturing center in the region but has suffered a decline in the late 20th century.