is a town in Meigs County, Tennessee, United States. The population was 1,395 at the 2000 census. It is the county seat of Meigs County.
Decatur is located at (35.518871, -84.793201). The town is situated at the western base of No Pone Ridge, an elongate ridge characteristic of the Appalachian Ridge-and-Valley Province. Just west of Decatur, the Tennessee River flows around a blunt peninsula known as Armstrong Bend. This section of the river is technically part of the river's Chickamauga Lake impoundment.
Decatur is centered around the junction of Tennessee State Route 30, which connects the town to Athens to the east and Dayton to the west, and Tennessee State Route 58, which connects Decatur to Kingston to the north and Chattanooga to the south. Interstate 75 passes approximately east of Decatur.
According to the United States Census Bureau, the town has a total area of 2.6 square miles (6.6 km²), all of it land.