 The general who won the last civil war of the Roman Republic , Gaius Octavian , became the master of the state . In the years after 30 BC , Octavian set out to reform the Roman constitution , and to found the Principate . The ultimate consequence of these reforms was the abolition of the republic , and the founding of the Roman Empire . Octavian was given the honorific Augustus ( " venerable " ) by the Roman Senate , and became known to history by this name , and as the first Roman Emperor . Octavian 's reforms did not , at the time , seem drastic , since they did nothing more than reorganize the constitution . The reorganization was revolutionary , however , because the ultimate result was that Octavian ended up with control over the entire constitution , which itself set the stage for outright monarchy . When Diocletian became Roman Emperor in 284 , the Principate was abolished , and a new system , the Dominate , was established . This system survived until the ultimate fall of the Eastern Roman ( Byzantine ) Empire in 1453 . 
