Much, if not all, of what is today Tajikistan had been part of the Achaemenid Empire, which Alexander the Great subdues in the fourth century BCE; it now becomes part of the Greco-Bactrian kingdom, one of the successor states to Alexander's empire.

The northern part of what is now Tajikistan is part of Sogdia, a distinct region that intermittently exists as a combination of separate oasis states and sometimes is subject to other states.