Byzantine Empire under the Theodosian dynasty

Roman Empire
379–457
Flag of Byzantium
The territory of the Eastern Roman Empire, with the Western Roman Empire depicted in orange, at the beginning of Theodosius I's reign.
The territory of the Eastern Roman Empire, with the Western Roman Empire depicted in orange, at the beginning of Theodosius I's reign.
CapitalConstantinople
Common languagesLatin, Greek
GovernmentMonarchy
Emperor 
• 379–395
Theodosius I
• 395–408
Arcadius
• 408–450
Theodosius II
• 450–457
Marcian
History 
• accession of Theodosius I
19 January 379
• death of Marcian
January 457
Preceded by
Succeeded by
Byzantine Empire under the Constantinian and Valentinianic dynasties
Byzantine Empire under the Leonid dynasty

The Eastern Roman Empire was ruled by the Theodosian dynasty from 379, the accession of Theodosius I, to 457, the death of Marcian. The rule of the Theodosian dynasty saw the final East-West division of the Roman Empire, between Arcadius and Honorius in 395. Whilst divisions of the Roman Empire had occurred before, the Empire would never again be fully reunited. The reign of the sons of Theodosius I contributed heavily to the crisis that under the fifth century eventually resulted in the complete collapse of western Roman court.

The Eastern Empire was largely spared the difficulties faced by the West in the third and fourth centuries, due in part to a more firmly established urban culture and greater financial resources, which allowed it to placate invaders with tribute and pay foreign mercenaries. Throughout the fifth century, various invading armies overran the Western Empire but spared the east.

The Theodosian dynasty also ruled the Western Roman Empire from 392 to 455 AD.