Caesar Augustus (born Gaius Octavius; 23 September 63 BC – 19 August AD 14), also known as Octavian, was the founder of the Roman Empire; he reigned as the first Roman emperor from 27 BC until his death in AD 14.[a] The reign of Augustus initiated an imperial cult as well as an era associated with imperial peace, the Pax Romana or Pax Augusta, in which the Roman world was largely free of armed conflict aside from expansionary wars and the Year of the Four Emperors. The Principate system of imperial rule established by Augustus lasted until the Crisis of the Third Century.