Hartsville is a town in Trousdale County, Tennessee, United States. It is the county seat of Trousdale County, with which it shares a consolidated city-county government. The population of Hartsville was 11,615 as of 2020. Hartsville now shares with Trousdale County a consolidated city-county government by virtue of a referendum which passed in Trousdale County in 2000. Despite the city-county government, under Tennessee law, Hartsville is also considered to be a distinct municipality.