Which region was called Transoxiana in the ancient times?

Transoxiana or Transoxania (Land beyond the Oxus) is the Latin name for a 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. Geographically, it is the region between the rivers Amu Darya to its south and the Syr Darya to its north.

Transoxiana's major cities and cultural centers are Samarkand and Bukhara. Both are in the southern portion of Transoxiana (though still to the north of the Amu Darya itself, on the river Zarafshan) and Uzbekistan, and the majority of the region was dry but fertile plains.