The South Newport River is a 42.6 mi river on the Atlantic coastal plain in the U.S. state of Georgia. It rises in Long County 3 mi south of Walthourville and flows east-southeast, becoming the boundary between Liberty and McIntosh counties. It flows into Sapelo Sound, an arm of the Atlantic Ocean, south of St. Catherines Island. The river's name most likely is a transfer from Newport, Rhode Island.