Little is known of the history of the peoples that inhabited the area of modern Romania. Archaeology gives us some knowledge of various cultures differentiated by their remains that can be found such as pottery and burials.
Scant documentary information starts when the Greeks first started trading along the Black Sea coast. Greek and Roman documents give a confusing picture of peoples they called Thracians, Getae and Dacians. It is not known how they were related, and if the Getae were Thracians or early Dacians.
The small amount of linguistic data classifies the Dacians, Thracians and Illyrians as having Indo-European languages. It is likely that the languages are related, but there is insufficient information on the Dacian language to be more precise. The Albanian language is thought to be derived from one of these earlier languages and the Romanian language contains some 160 words from this language group.
Vladimir Georgiev studied the distribution of place names to determine the extent of Thracian and Dacian populations. Toponyms formed from -dava are derived from the Dacian for city or fort, and -para are derived from Thracian. The Thracian toponyms of -para for village, -bria for town and -diza for fortruss all lie south of the Danubian plain suggesting that Thrace only extended north to the Balkan mountains.
The best known Dacian king were Dromihetes, Burebista and Decebalus who organized powerful states and proved to be skilful military strategists. The Dacian king reigned with the help of a council of noblemen and with the advice of the high priest.
Dromihetes is known due to his conflict around 300 BC with Lisimah, a general of Alexander the Great who became king of Thrace after Alexander's death. Lisimah attempted to extend his kingdom to the north of the Danube, but Dromihetes wanted Lisimah to return some fortresses from the south of the Danube. Dromihetes won all of the battles capturing Agatocles, the son of Lisimah. Dromihetes won again in 292 BC when Lisimah took his army across the Danube. Dromihetes' capital was Helis which is generally thought to have been in Muntenia. Other kings in this period were Zalmodegicos and Rhemaxos of Dobrogea and Oroles of Transylvania.
Burebista reigned from 82 BC to around 44 BC, probably inheriting the position from his father. The kingdom of Burebista included all the Dacian tribes, plus some others. When Burebista offered to support Pompey against Caesar (48 BC) his kingdom stretched from the Beskids mountains in the north, the Middle Danube in the west, the river Dniester in the east, and to the Balkan Mountains in the south. Burebista developed a system of fortifications in the Orastie mountains as a natural stronghold. Burebista notable military campaigns were:
- 60-59 BC - successful against the Celts that were threatening Dacia from the north-west
- 55 BC - conquered the Greek cities on the Black Sea coast, from Olbia to Apollonia
- The retreat of the Scythians to the river Don
- after 48 BC - defeated the Celts to the north-west and the south-west of Dacia
The kingdom split into smaller kingdoms after Burebista's death. The kings reigning from Sarmizegetusa situated in the Orastie Mountains were Deceneu, Comosicus, Scorilo, and Duras.
Decebal reigned from 87 AD to 106 AD, having been given the throne from Duras. He was previously the leader nobleman of the Dacians at Tapae. He was originally called Diurpaneus, but took the name of Decebal meaning "the powerful one". Decebal's state was smaller than that of Burebista with the borders being the rivers Tisza in the west, Siret in the east, Danube in the south and the northern Carpathians.
The Dacian state was powerful enough to survive a confrontation with the Romans during the reign of Domitian (87-89). It took a further two fierce wars during 101 -102 AD and 105-106 AD for the Roman empire under Emperor Trajan (98-117) to defeat Decebal and turn most of his kingdom into the Roman province called Dacia.