The Mekong rises as the Lancang in the "Three Rivers Area" on the Tibetan Plateau in the Sanjiangyuan National Nature Reserve; the reserve protects the headwaters of, from north to south, the Yellow (Huang He), the Yangtze and the Mekong Rivers.[3] It flows southeast through Yunnan Province, and then through the Three Parallel Rivers Area in the Hengduan Mountains, along with the Yangtze to its north and the Salween River (Nujiang in Chinese) to its south.
The Mekong then meets the tripoint of China, Burma (Myanmar) and Laos. From there it flows southwest and forms the border of Burma and Laos for about 100 kilometres (62 mi) until it arrives at the tripoint of Burma, Laos, and Thailand. This is also the point of confluence between the Ruak River (which follows the Thai-Burma border) and the Mekong. The area of this tripoint is sometimes termed the Golden Triangle, although the term also refers to the much larger area of those three countries that is notorious as a drug producing region