The Constantinian dynasty is an informal name for the ruling family of the Roman Empire from Constantius Chlorus to the death of Julian in 363. It is named after its most famous member, Constantine the Great, who became the sole ruler of the empire in 324. The dynasty is also called Neo-Flavian because every Constantinian emperor bore the name Flavius, similarly to the rulers of the first Flavian dynasty in the 1st century.

The Roman Empire was the post-Republican state of ancient Rome. It is generally understood to mean the period and territory ruled by the Romans following Octavian's assumption of sole rule under the Principate in 27 BC. It included territories in Europe, North Africa, and Western Asia and was ruled by emperors. The fall of the Western Roman Empire in 476 AD conventionally marks the end of classical antiquity and the beginning of the Middle Ages.