Erwin is a town in and the county seat of Unicoi County, Tennessee, United States. The population was 5,610 at the 2000 census. It is part of the Johnson City Metropolitan Statistical Area, which is a component of the Johnson City–Kingsport–Bristol, TN-VA Combined Statistical Area – commonly known as the "Tri-Cities" region.
Erwin is located at 36°8′42″N 82°24′39″W / 36.145°N 82.41083°W / 36.145; -82.41083 (36.145036, -82.410796), beside the Nolichucky River.
According to the United States Census Bureau, the city has a total area of 3.5 square miles (9.2 km²), of which, 3.5 square miles (9.2 km²) of it is land and 0.28% is water.