Waccamaw River, river in southeastern North Carolina and eastern South Carolina, U.S., that rises in the Lake Waccamaw area of North Carolina. It flows southwest across the South Carolina border to join the Pee Dee River just before emptying into Winyah Bay near Georgetown, after a course of 140 miles (225 km). The Atlantic Intracoastal Waterway follows the lower course for about 30 miles (48 km).