Transoxiana or Transoxania is the Latin name for the region and civilization located in lower Central Asia roughly corresponding to modern-day eastern Uzbekistan, western Tajikistan, parts of southern Kazakhstan, parts of Turkmenistan and southern Kyrgyzstan. The name was first coined by Alexander the Great in the 4th century BC when Alexander's troops were able to conquer the region. The region may have had a similar Greek name in the days of Alexander the Great, but the earlier Greek name is no longer known. Geographically, it is the region between the rivers Amu Darya to its south and the Syr Darya to its north.

The Amu Darya, also called the Amu, the Amo, and historically the Oxus, is a major river in Central Asia, which flows through Tajikistan, Turkmenistan, Uzbekistan and Afghanistan. Rising in the Pamir Mountains, north of the Hindu Kush, the Amu Darya is formed by the confluence of the Vakhsh and Panj rivers, in the Tigrovaya Balka Nature Reserve on the border between Afghanistan and Tajikistan, and flows from there north-westwards into the southern remnants of the Aral Sea. In its upper course, the river forms part of Afghanistan's northern border with Tajikistan, Uzbekistan, and Turkmenistan. In ancient history, the river was regarded as the boundary of Greater Iran with Turan, which roughly corresponded to present-day Central Asia. The Amu Darya has a flow of about 70 cubic kilometres per year on average.