Transoxiana (sometimes spelled Transoxania) is the largely obsolete name used for the portion of Central Asia corresponding approximately with modern-day Uzbekistan and southwest Kazakhstan. Geographically, it means the region between the Amu Darya and Syr Darya rivers. When used in the present, it usually implies that one is talking about that region in the time prior to about the 8th century CE, although the term continued to remain in use among western historians for several centuries after.

The name, however, is Latin, and literally means "beyond the Oxus River", an older name for the Amu Darya, which describes the region perfectly from the viewpoint of the Greeks and Romans. The name stuck in Western consciousness because of the exploits of Alexander the Great, who extended Greek culture into the region with his conquests of the 4th century BCE; Transoxiana represented the uttermost northeastern point of the Hellenistic culture, and in fact kept a hybrid Greek/Indian/Chinese Buddhist culture, dubbed 'Serindian ', until the Islamic conquest. During this time, when Transoxiana was cut off from the rest of Western culture by the Sassanid Empire, it is often called Sogdiana, a provincial name taken from early Persian, and used to distinguish it from nearby Bactria.

Transoxiana's major city and cultural center was Samarkand, while another was Bukhara. Both are in the southern portion of Transoxiana, however (though still to the north of the Oxus itself, on the river Zeravshan), and the majority of the region was dry but fertile plains.

Following the Arab conquest of this area, it became known as Ma wara'un-Nahr (Arabic, "what is beyond the river").

Genghis Khan invaded Transoxiana in 1219 during his conquest of Khwarazm. Before his death in 1227, he assigned the lands of Western Central Asia to his second son Chagatai, and this region became known as the Chagatai Khanate. In 1369 Tamerlane, of the Barlas tribe, became a ruler under the authority of Chigatay Khan's dynasty, and he made Samarkand the capital of his future empire.