Gallatin is a city in and the county seat of Sumner County, Tennessee, United States. The population was 30,278 at the 2010 census and 44,431 at the 2020 census. Named for United States Secretary of the Treasury Albert Gallatin, the city was established on the Cumberland River and made the county seat of Sumner County in 1802. It is located about 30.6 miles northeast of the state capital of Nashville, Tennessee.