South Uist is an island parish, which lies in the Western Isles Council Area, some 44 miles (71 km) west of Portree in Highland and 49 miles (78 km) southwest of Tarbert in the Western Isles and includes 2 other small offshore islands.
It is located in the old county of Invernessshire, which disappeared following the Local Government (Scotland) Act 1974.
The parish has an area of 320.9 sq. km (123.9 sq. miles).