The Dark Ages in Romania began with the withdrawl of the Roman administration. Faced by successive invasions of Goths and Carpians, the Roman administration withdrew from Dacia, abandoning the last of their positions north of the Danube during the reign of Aurelian (270-275).
The withdrawal of the Romans gave the opportunity to people pressing the empire boundaries to occupy the areas left by the Roman legions, leading to the so called Great Migrations that separated Antiquity from the Middle Ages in Europe.

This period is further divided into two phases. The first phase, from 300 to 500, saw the movement of Germanic and other tribes (Ostrogoths, Visigoths, Burgundians, Suebi, Alamanni Marcomanni) following the migration of the Huns from Mongolia to Western Europe and ended with the settlement of these peoples in the areas of the former Western Roman Empire. Concerning nowadays Romania, Visigoths ruled in 275–376 and at the end of the 4th century to 454 it became part of the Kingdom of the Huns under Attila (406 - 453).

The second phase, between 500 and 900, saw the re-settling of the German tribes at the end of the Hunnish expansion in Eastern Europe and gradually making it predominantly Slavic. In particular, the Huns were supplanted by the Germanic Gepids (454–567) in the Pannonian plain, defeated in 567 by the Avars, opening the way for a massive advance of Slavs into the region.
The last phase of the migrations saw the coming of the Magyars to the Pannonian plain leaded by Árpád (850 - 907). Hungarian settlement in the Carpathian bacin became approved by the Pope Silvester II by the crowning of Stephen I of Hungary in 1001 when the leaders accepted Christianity.
Byzantine Empire held from time to time, (such as during Justinian's reign in the 6th century or again under the emperors of the Macedonian dynasty 9th-10th centuries) the territory of today's Dobruja, but it was a border that was hard to keep due to the constant invasions from the north. In 971, the Byzantine Empire reestablished its dominance north of the Danube and in Dobruja, being part of the Paristrion province between 971 and 1204.
The Romanians to the south of the Danube were the first to be mentioned in historical sources (the 10th century), under the name of vlahi or blahi (Wallachians); this name given by the non-Roman peoples around them means that they were speakers of a Romance language.
The Romanian language was submitted to a long evolutionary process. The main hypothesis consider this language starting from the vulgar Latin spoken by the population during the Roman presence in the region, even if some sources depict an independent evolution of the Dacian language from the Latin, coming from the common Indo-European roots.
The process ended by the end of the 1st millennium. The grammar structure of the Romanian language is Latin and it is formed of a basic lexical stock of 60% of Latin words, to which we have to add the words that come from the Daco-Getic substratum, as well as 15-20% of Slavic words.
When the formation process of the Romanian people was done, this nation emerged as a Christian one. The Romanians belonged to the Orthodox religion and they adopted the Old Church Slavic as a cult language.
This evolution was made possible by the work of Saints Cyril (827 - 869) and Methodius (826 - 885), who translated the Bible and many of the prayer books into Slavonic developping the Cyrillic alphabet and were sent to evangelize to the Slavs in Great Moravia by Byzantine Emperor Michael III (842 - 847).