Augustus (Classical Latin: [awˈɡʊstʊs], English: /ɔːˈɡʌstəs/; Latin: Imperator Gaius Julius Caesar Augustus; 23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD. Born Gaius Octavius Thurinus, he was adopted posthumously by his great-uncle Gaius Julius Caesar in 44 BC via his last will and testament, and between then and 27 BC was officially named Gaius Julius Caesar. In 27 BC the Senate awarded him the honorific Augustus ("the revered one"), and thus consequently he was Gaius Julius Caesar Augustus.

The young Octavius came into his inheritance after Caesar's assassination in 44 BC. In 43 BC, Octavian joined forces with Mark Antony and Marcus Aemilius Lepidus in a military dictatorship known as the Second Triumvirate. As a triumvir, Octavian ruled Rome and many of its provinces. The triumvirate was eventually torn apart under the competing ambitions of its rulers: Lepidus was driven into exile, and Antony committed suicide following his defeat at the Battle of Actium by Octavian's fleet under the command of Agrippa in 31 BC.