McDonough is a city in Henry County, Georgia, United States. It is part of the Atlanta metropolitan area. Its population was 22,084 at the 2010 census, up from 8,493 in 2000. The city is the county seat of Henry County. The unincorporated communities of Blacksville, Flippen, Kelleytown, and Ola are located near McDonough, and addresses in those communities have McDonough postal codes.