Hardin County is a county located in the U.S. state of Tennessee. As of the 2020 census, the population was 26,831. The county seat is Savannah. Hardin County is located north of and along the borders of Mississippi and Alabama. The county was founded in November 1819 and named posthumously for Col. Joseph Hardin, a Revolutionary War soldier and a legislative representative for the Province of North Carolina; the State of Franklin; and the Southwest Territory.