Round O (formerly also called Round) is an unincorporated community in Colleton County, South Carolina, United States. The population of Round O is 2,136 people. Its elevation is 36 feet (11 m). It is located near the intersection of Cottageville Highway (US 17 Alt.) and Round O Road. According to tradition, the community received its name from a local Native American whose name was too long to pronounce, hence the name Round O, and painted his torso with a circular design.