Margiana is a region within the Achaemenid satrapy of Bactria, and a province within its successors, the Seleucid, Parthian and Sasanian Empires.It is located in the valley of the Murghab River which has its sources in the mountains of Afghanistan, and passes through Murghab District in modern Afghanistan, and then reaches the oasis of Merv in modern Turkmenistan.

Margiana borders Parthia in the west, Aria in the south, Bactria in the east and Sogdia in the north.