South China Sea, arm of the Pacific Ocean, located off the eastern and southeastern coasts of Asia. On the north, it is divided from the East China Sea by Taiwan and the Taiwan Strait. It is partly enclosed on the east by the Philippines and Borneo. In the southwest it merges with the Gulf of Thailand (Siam), and on the west it is separated from the Gulf of Tonkin by the Chinese island of Hainan. The South China Sea increases in depth from the south, where much of it is less than 300 m (1,000 ft) deep, to the north, where depths of 4,600 m (15,000 ft) have been found. The total area of the sea is 2,319,000 sq km (895,400 sq mi). The chief ports on or near this sea include Manila, Singapore, Bangkok, Ho Chi Minh City (formerly Saigon), Hong Kong, and Macao. The principal rivers draining into the South China Sea are the Mekong and the Xi Jiang. Shipping and fishing in the sea are economically important. Weather in the region is marked by violent monsoons and typhoons.

The Spratlys, a chain of islands with reportedly vast oil reserves, are located in the South China Sea between Vietnam and the Philippines. Since the 1950s, the islands have been the subject of a territorial dispute among several Asian nations, including China, Vietnam, Taiwan, the Philippines, Malaysia, and Brunei.