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.

Central Asia is a subregion of Asia that stretches from the Caspian Sea in the southwest and Eastern Europe in the northwest to Western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, and Uzbekistan. The countries as a group are also colloquially referred to as the "-stans" as all have names ending with the Persian suffix "-stan" in both respective native languages and most other languages.