Augustus Caesar, first Roman Emperor. Gaius Julius Caesar Octavianus (63 BC14 AD) became one of a triumvirate of rulers after the death in 44 BC of Julius Caesar, his greatuncle, whose dictatorship had brought an end to the Roman republic. He became sole ruler in 31 BC after defeating Mark Anthony at the Battle of Actium, and in 27 BC proclaimed himself Emperor, adopting the title Caesar Augustus. Octavians rule, which lasted until 14 AD, ended a century civil strife and was a period of peace and prosperity in which Rome attained the height of its imperial power. Marble statue in the Vatican, Rome.