Oxus, the ancient name of the Amu or Amu-Daria, a river in western Asia, called by Arab writers the Jihun. It rises in the elevated tablelands between the Tian-Shan Mountains and the Hindu-Kush, and flows west as far as 66° E. long. through Badakshan, and then north-west through Bokhara and Khiva, and empties itself by several mouths into the southern end of the Sea of Aral. There are two main head-streams issuing at 13,042 and 14,177 feet respectively, and uniting in 71° 20' E. long. at 7500 feet. The Oxus receives few tributaries after it turns north-west, its course then running through the deserts of Turkestan. The delta is 90 miles long, and embraces many lakes and marshes. The principal use made of the river is for irrigation; Khiva owes its prosperity to its waters. In 1894 it was navigated by a Russian steamer as far as Faizabad Kali on the Afghan frontier. It is believed that before the Christian era the Oxus flowed into the Caspian, and that since 600 a.d. it has twice changed its course. Between Merv and Bokhara it is spanned by a railway viaduct (1888), 6804 feet long. See works by J. Wood (1841; new ed. by Colonel Yule, 1872) and MacGahan (1876).