The Altamaha River /ˈɑːltəməhɑː/ is a major river in the U.S. state of Georgia. It flows generally eastward for 137 miles (220 km) from its origin at the confluence of the Oconee River and Ocmulgee River towards the Atlantic Ocean, where it empties into the ocean near Brunswick, Georgia. There are no dams directly on the Altamaha, though there are some on the Oconee and the Ocmulgee. Including its tributaries, the Altamaha River's drainage basin is about 14,000 square miles (36,000 km2) in size, qualifying it among the larger river basins of the US Atlantic coast. It is reportedly the third largest contributor of fresh water to the Atlantic Ocean from North America. Including its longest tributary (the Ocmulgee River) in length calculations as is standard USGS practice, its length of 470 miles (760 km) places it seventh on the list of U.S. rivers entirely within one state, behind only four Alaskan rivers, the Sacramento-Pit River in California, and the Trinity River in Texas. The beginning of the Colorado River of Texas is just within New Mexico. The long Mobile-Alabama-Coosa River system, mostly in Alabama, originates a short distance within Georgia.
The Altamaha River traverses a broad area of low population density with few significant towns or cities along its course. There are some along its upper tributaries, such as the fall line cities of Milledgeville on the Oconee and Macon on the Ocmulgee. Centuries ago, riverboats used the Altamaha to reach those towns and the plantations founded along the rivers, which were the main transportation routes.
According to the USGS, variant and historical names of the Altamaha River include A-lot-amaha, Alatahama, Alatamaha, Allamah, Frederica River, Rio Al Tama, Rio de Talaje, and Talaxe River.
The 1,759-megawatt Plant Hatch nuclear power plant sits on the southern bank of the Altamaha River in Appling County. A Rayonier paper mill that manufactures cellulose fibers used in plastics and absorbent materials for diapers, tampons and other products is located on the southern bank of the Altamaha River in Wayne County.