Roman Dacia (also Dacia Traiana and Dacia Felix) was a province of the Roman Empire from 106 to 274–275 AD. Its territory consisted of eastern and south-eastern Transylvania, the Banat, and Oltenia (regions of modern Romania). It was from the very beginning organized as an imperial province and remained so throughout the Roman occupation. Historians' estimates of the population of Roman Dacia range from 650,000 to 1,200,000.

The conquest of Dacia was completed by Emperor Trajan (98–117) after two major campaigns against Decebalus' Dacian kingdom. The Romans did not occupy the entirety of the old Dacian kingdom, as the greater part of Moldavia, together with Maramureș and Crișana, was ruled by Free Dacians even after the Roman conquest. In 119, the Roman province was divided into two departments: Dacia Superior (Upper Dacia) and Dacia Inferior (Lower Dacia) (later named Dacia Malvensis). In 124 (or around 158), Dacia Superior was divided into two provinces: Dacia Apulensis and Dacia Porolissensis. During the Marcomannic Wars the military and judicial administration was unified under the command of one governor, with another two senators (the legati legionis) as his subordinates; the province was called tres Daciæ (Three Dacias) or simply Dacia.

Dacia may refer to:

Historic geography

Modern places