augustus
Full names:
Gaius Octavius Thurinus (before his adoption by Julius Caesar)
Gaius Julius Caesar (after adoption. Same as his great-uncle). Usually called "Octavian" by historians to avoid confusion with his uncle.
Caesar's heir and first emperor of Rome. Founded the Roman Empire. His reign was an era of relative peace known as the Pax Romana.
Augustus is his title, and is how historians refer to him after he obtained said title starting 27 BC.