Southborough is an affluent town in Worcester County, Massachusetts, United States. It incorporates the smaller villages of Cordaville, Fayville, and Southville. Its name is often informally shortened to Southboro, a usage seen on many area signs and maps, though officially rejected by town ordinance. Its population was 9,767 at the 2010 census, in nearly 3,000 households.First settled in 1660, land use now is primarily residential, with substantial open space. A tenth of the town's area is flooded by the Sudbury Reservoir.