Salween River much of its length, the Salween's course is nearly parallel to that of the much larger Mekong in the east. Although the commonly accepted name is Salween, the river is known by a handful of other names regionally: "Nu" in China, "Thanlwin" in southern Burma, and "Salawin" on the border of Thailand and Burma. Several major sub-continental drainage basins border on the Salween. The Mekong basin forms nearly the entire eastern boundary of the watershed, while the Irrawaddy River flows southwards on the west side of the basin. The smallest boundary is formed by the Yangtze to the extreme north.
Salween River National Park to join the Moei River from the east as it approaches Thailand, where it is called the "Salawin", forming the Burma-Thailand boundary for about , before re-entering Burma, passing through Karen State and Mon State. The river finally breaks out of its gorge about from the mouth, and slows down dramatically as it courses through a series of agricultural valleys. About from the mouth the river finally widens and deepens enough to become navigable for large watercraft. In quick succession it receives Dontham River from the right and Gyaing River from the left, from where the river turns