The previous Roman Republic , which had replaced Rome 's monarchy in the 6th century BC , became severely destabilized in a series of civil wars and political conflict . In the mid-1st century BC Julius Caesar was appointed as perpetual dictator and then assassinated in 44 BC . Civil wars and proscriptions continued , culminating in the victory of Octavian , Caesar 's adopted son , over Mark Antony and Cleopatra at the Battle of Actium in 31 BC . The following year Octavian conquered Ptolemaic Egypt , ending the Hellenistic period that had begun with the conquests of Alexander the Great of Macedon in the 4th century BC . Octavian 's power was then unassailable and in 27 BC the Roman Senate formally granted him overarching power and the new title '' Augustus '' , effectively making him the first emperor
assassinated
Assassination of Julius Caesar
Roman Empire