Rome was founded (by tradition) in 753 BC, became a Republic in 509 BC, and became an empire in 27 BC under Augustus. The Western Roman Empire fell in 476 AD; the Eastern (Byzantine) Empire carried the Roman name until 1453 AD.
"The Roman Empire" is really the middle act of a much longer story. Rome spent its first two and a half centuries as a kingdom, then nearly 500 years as a republic, and only then became the empire of Caesars that most people picture. Here is the whole arc, in order.
The four eras at a glance
| Era | Dates | Who ruled |
|---|---|---|
| Roman Kingdom | 753–509 BC | Seven legendary kings |
| Roman Republic | 509–27 BC | Senate and elected magistrates |
| Roman Empire (united) | 27 BC–395 AD | Emperors, from Augustus onward |
| Western Roman Empire | 395–476 AD | Western emperors (ended 476) |
| Eastern / Byzantine Empire | 395–1453 AD | Eastern emperors at Constantinople |
Key dates in the Roman timeline
| Date | What happened |
|---|---|
| 753 BC | Traditional founding of Rome, tied to the legend of Romulus. |
| 509 BC | The last king is overthrown; the Roman Republic is established. |
| 264–146 BC | The three Punic Wars against Carthage; Rome becomes the master of the Mediterranean. |
| 49 BC | Julius Caesar crosses the Rubicon, starting a civil war. |
| 44 BC | Caesar is assassinated on the Ides of March. |
| 27 BC | Octavian is named Augustus. The Roman Empire begins. |
| 80 AD | The Colosseum opens with 100 days of games. |
| 117 AD | Under Trajan, the empire reaches its greatest size. |
| 122 AD | Construction of Hadrian's Wall begins in Britain. |
| 212 AD | Citizenship is extended to nearly every free person in the empire. |
| 235–284 AD | The Crisis of the Third Century: civil war, plague, and dozens of emperors. |
| 313 AD | The Edict of Milan grants toleration to Christianity. |
| 330 AD | Constantine dedicates Constantinople as a new capital. |
| 395 AD | The empire is permanently divided into East and West. |
| 410 AD | The Visigoths sack the city of Rome. |
| 476 AD | The last western emperor, Romulus Augustulus, is deposed. The West falls. |
| 1453 AD | Constantinople falls to the Ottomans. The Eastern Roman Empire ends. |
Kingdom and Republic (753–27 BC)
Rome began as a small city ruled by kings. When Romans overthrew their last king around 509 BC, they built a republic designed to prevent any one man from holding too much power: two annually elected consuls, a Senate of former magistrates, and popular assemblies. Over the next four centuries that republic conquered Italy, then defeated Carthage in the Punic Wars, and expanded around the Mediterranean.
Success strained the system. Generals grew more powerful than institutions, and a century of civil wars followed. Julius Caesar came out on top, was made dictator for life, and was assassinated in 44 BC by senators who feared he had become a king in all but name.
The Empire begins (27 BC)
Caesar's heir, Octavian, won the wars that followed and, in 27 BC, accepted the title Augustus. He kept the outward forms of the Republic while holding real power himself, which is why historians mark 27 BC, not Caesar's lifetime, as the true start of the Roman Empire. What followed was the Pax Romana, roughly two centuries of relative stability across the Mediterranean world.
Peak and crisis (117–284 AD)
The empire reached its largest extent in 117 AD under Trajan, stretching from northern Britain to the Persian Gulf region. The 3rd century was far harder: the Crisis of the Third Century brought plague, invasions, runaway inflation, and a blur of short-lived emperors, several of whom ruled only months.
Division and the fall of the West (395–476 AD)
Diocletian and later Constantine steadied the empire, and Constantine founded a second capital, Constantinople, in the east. In 395 the empire was split for good into western and eastern halves. The West, poorer and more exposed, buckled under pressure from migrating peoples. In 476 AD the last western emperor was deposed, the conventional end date for "the fall of Rome."
The East lived on (until 1453)
Here is the part most timelines leave out: the Roman Empire did not vanish in 476. Its eastern half, centered on Constantinople and known today as the Byzantine Empire, kept calling itself Roman for another thousand years. It only ended in 1453, when Constantinople fell to the Ottoman Turks. By that measure, the Roman state lasted almost 1,500 years.
Sources: standard chronologies of Roman history; dates for the founding (753 BC) and the Republic (509 BC) follow Roman tradition and are approximate. The end date of 476 AD is a historical convention, not a moment when Rome literally disappeared.
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