Jonesborough (historically also Jonesboro) is a town in, and the county seat of, Washington County, Tennessee, in the Southeastern United States. Its population was 5,860 as of 2020. It is "Tennessee's oldest town". Jonesborough is part of the Johnson City metropolitan statistical area, which is a component of the Johnson City–Kingsport–Bristol, TN and VA combined statistical area – commonly known as the "Tri-Cities" region.