Blountville is a census-designated place (CDP) in Sullivan County, Tennessee, United States. The population was 2,959 at the 2000 census. It is the county seat of Sullivan County and is the only Tennessee county seat not to be an incorporated city or town. Blountville is part of the Kingsport–Bristol (TN)–Bristol (VA) 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.