Orange River, the chief river of South Africa. It begins on the slopes of the Drakensberg range in northeastern Lesotho and flows generally westward for 1,300 miles (2,100 km) across Lesotho and South Africa to the Atlantic Ocean. The river serves as the boundary between the countries of South Africa and Namibia. It also forms parts of the boundaries of several provinces in South Africa. Its principal tributary is the Vaal River.

Falls and rapids mark some sections of the Orange. Most impressive is 620-foot (189-m) Augrabies Falls in western Cape Province.

The Orange River system has been developed by the South African government to provide water for irrigation, hydroelectric power, and urban use. Three dams, their reservoirs, and a 52-mile (84-km) tunnel are basic elements of the project. There is virtually no navigation on the river.