Dacia (, DAY-shə; Latin: [ˈd̪aː.ki.a]) was the land inhabited by the Dacians, its core in Transylvania, stretching to the Danube in the south, the Black Sea in the east, and the Tisza in the west. The Carpathian Mountains were located in the middle of Dacia. It thus roughly corresponds to the present-day countries of Romania, as well as parts of Moldova, Bulgaria, Serbia, Hungary, Slovakia, and Ukraine.

A Dacian kingdom of variable size existed between 82 BC until the Roman conquest in AD 106, reaching its height under King Burebista. As a result of the two wars with Emperor Trajan, the population was dispersed and the central city, Sarmizegetusa Regia, was destroyed by the Romans, but was rebuilt by the latter to serve as the capital of the Roman province of Dacia. A group of "Free Dacians," may have remained outside the Roman Empire in the territory of modern-day Northern Romania until the start of the Migration Period.