Nam Theun (also known as Khading), is a river in Laos, in Khammouane and Bolikhamsai Provinces. Together with its tributaries Nam One, Nam Noy, and Nam Theun it has total length of 138 km (86 mi) [a] and drains an area of 2,800 km2 (1,100 sq mi). "Nam Theun" is also three options for large dams on the same river, called Nam Theun 1, Nam Theun 1-2 and Nam Theun 2. Nam Theun 2, which was considered the most economic of the three options, is in operation.
^The length of 138 km (86 mi) is only from the mouth in Pakkading District to Nam Theun 2. The actual length should be c. 280 km (170 mi), to the Nakai–Nam Theun NBCA at the border to Vietnam.