The Gulf of Thailand, historically known as the Gulf of Siam, is a shallow inlet in the southwestern South China Sea, bounded between the southwestern shores of the Indochinese Peninsula and the northern half of the Malay Peninsula. It is around 800 km (500 mi) in length and up to 560 km (350 mi) in width, and has a surface area of 320,000 km² (120,000 sq mi). The gulf is surrounded on the north, west and southwest by the coastlines of Thailand, on the northeast by Cambodia and the Mekong Delta region of Vietnam, and opens to the South China Sea in the southeast.