The Roman Empire[a] was the post-Republican state of ancient Rome. It included territory around the Mediterranean in Europe, North Africa, and Western Asia, and was ruled by emperors. The adoption of Christianity as the state church in 380 and the fall of the Western Roman Empire conventionally marks the end of classical antiquity and the beginning of the Middle Ages.
Rome had expanded its rule to most of the Mediterranean and beyond, but became severely destabilized in civil wars and political conflicts which culminated in the victory of Octavian over Mark Antony and Cleopatra at the Battle of Actium in 31 BC and the subsequent conquest of the Ptolemaic Kingdom in Egypt. The Roman Senate granted Octavian overarching power (imperium) and the new title of Augustus, marking his accession as the first Roman emperor of a monarchy with Rome as its sole capital. The vast Roman territories were organized in senatorial and imperial provinces.
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