Decatur is a city in, and county seat of, DeKalb County, Georgia, United States. With a population of 20,148 in the 2013 census, the municipality is sometimes assumed to be larger since multiple zip codes in unincorporated DeKalb County bear the Decatur name. It is an intown suburb of Atlanta and part of the Atlanta metropolitan area, and its public transportation is served by three MARTA rail stations.