river formed by the confluence of the Tugaloo and Seneca rivers at Hartwell Dam, Georgia, U.S. It constitutes the boundary between Georgia and South Carolina as it flows southeastward past Augusta and Savannah, Ga., into the Atlantic Ocean after a course of 314 miles (505 km). Its chief tributaries are the Broad and Little rivers (north of Augusta) and Brier Creek (south of Augusta). The Savannah River is navigable for shallow draft and barge traffic from its mouth to Augusta and for ocean vessels from the mouth to 5 miles (8 km) above Savannah. The river is used extensively for hydroelectric, flood-control, and navigation purposes. Dams and reservoirs include Hartwell and Clark Hill near Augusta. The U.S. Nuclear Regulatory Commission's Savannah River Plant is in Aiken and Barnwell counties in South Carolina, down the river from Augusta. The Intracoastal Waterway crosses Savannah Harbor just below the port city of Savannah, which is the site of a large naval-stores centre and of docks operated by the Georgia Ports Authority.

Early Spanish explorers called the river Río Dulce (“Sweet River”), and its Indian name was Isondega (“Blue Water”); the name Savannah was probably derived from the Spanish sabana (“flat country”) or from the Sawana Indians.