Athens is a city in, and the county seat of, Athens County, Ohio, United States. A historic college town in the southeastern part of the state, Athens is home to Ohio University and is the principal city of the Athens, Ohio Micropolitan Statistical Area. The population was 21,342 in the 2000 census; it was estimated to be 21,909 in 2007. Athens is a qualified Tree City USA by the National Arbor Day Foundation.