Chemung County is a county located in the U.S. state of New York. It is part of the 'Elmira, New York Metropolitan Statistical Area' which encompasses all of Chemung County. As of the 2010 census, the population was 88,830. Its name is derived from the name of a Delaware Indian village (meaning "big horn"). Its county seat is Elmira. Many signs posted along roads in Chemung County refer to the area as "Mark Twain Country" because of the many years the author lived and wrote in Elmira.
Chemung County was formed from of Tioga County in 1836.
In 1854, Chemung County was divided and became Schuyler County, reducing Chemung to , its current size.