Lithonia is a city in eastern DeKalb County, Georgia, United States. The city's population was 2,662 at the 2020 census. Lithonia is in the Atlanta metropolitan area. "Lithonia" means "city/town of stone". Lithonia is in the heart of the Georgian granite-quarrying and viewing region, hence the name of the town, from the Greek lithos, for “stone”. The huge nearby Stone Mountain is composed of granite, while the Lithonia gneiss is a form of metamorphic rock.