The Dacians were the ancient Indo-European inhabitants of the cultural region of Dacia, located in the area near the Carpathian Mountains and west of the Black Sea. They are often considered a subgroup of the Thracians. This area includes mainly the present-day countries of Romania and Moldova, as well as parts of Ukraine, Eastern Serbia, Northern Bulgaria, Slovakia, Hungary and Southern Poland. The Dacians and the related Getae spoke the Dacian language, which has a debated relationship with the neighbouring Thracian language and may be a subgroup of it. Dacians were somewhat culturally influenced by the neighbouring Scythians and by the Celtic invaders of the 4th century BC.

Dacia 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 present-day Romania, as well as parts of Moldova, Bulgaria, Serbia, Hungary, Slovakia, and Ukraine.