In ancient geography, especially in Roman sources, Dacia is the land inhabited by the Dacians or Getae as they are known by the Greeks—a branch of the Thracians north of the Haemus range.Dacia is bounded in the south approximately by the Danubius river (Danube), in Greek sources the Istros, or at its greatest extent, by the Haemus Mons (the Balkan Mountains).

Moesia (Dobrogea), a region south of the Danube, is a core area where the Getae live and interact with the Ancient Greeks.

In the east it is bounded by the Pontus Euxinus (Black Sea) and the river Danastris (Dniester), in Greek sources the Tyras.

But several Dacian settlements are recorded between the rivers Dniester and Hypanis (Bug River), and the Tisia (Tisza) to the west.At times Dacia includes areas between the Tisza and the Middle Danube.

The Carpathian Mountains are located in the middle of Dacia.

It thus corresponds to the present day countries of Romania and Moldova, as well as smaller parts of Bulgaria, Serbia, Hungary, and Ukraine.Dacians (or Getae) are North Thracian tribes.

Dacian tribes have both peaceful and military encounters with other neighboring tribes, such as Celts, Ancient Germans, Sarmatians, and Scythians, but are most influenced by the Ancient Greeks and Romans.

The latter eventually conquer, and linguistically and culturally assimilate, the Dacians.A Dacian Kingdom of variable size exists between 82 BCE until the Roman conquest in 106 CE.

The capital of Dacia, Sarmizegetusa, located in modern Romania, is destroyed by the Romans, but its name is added to that of the new city (Ulpia Traiana Sarmizegetusa) built by the latter to serve as the capital of the Roman province of Dacia.