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.

Trousdale County, also known as Hartsville/Trousdale County, is a county in the U.S. state of Tennessee. As of the 2020 census, the population was 11,615. Its county seat is Hartsville, with which it shares a uniquely formed consolidated city-county government. With an area of just 117 square miles (300 km2), it is Tennessee's smallest county.