The Roman Republic was ruled by elected officials and the Senate, and the Roman Empire by an emperor. Tradition dates the change to 27 BC, when Augustus took power. Rome ruled lands overseas under both, so the difference is how it was governed, not whether it had an empire.
Key takeaways
- The Republic had two consuls elected each year, and the Empire had one ruler, the emperor, who held effectively all meaningful authority.
- The change is dated to 27 BC, when the Senate gave Octavian the name Augustus, but it was a slow shift and not a single day.
- Rome already held 13 provinces by 133 BC, long before the first emperor.
- The map's biggest outline, 4.88 million km² in AD 117, belongs to the Empire, but the Republic had reached 1.97 million km² by 44 BC.
How the Republic and the Empire differ
The Roman Republic and the Roman Empire are two ways Rome was governed, one after the other. In the Republic, power was spread between officials who were elected for a year, with the Senate advising them. In the Empire, one ruler, the emperor, held effectively all meaningful authority, while the old offices carried on in name [2].
The traditional dividing line is 27 BC. Julius Caesar had been named dictator for life in 44 BC and was assassinated the same year [1]. His heir Octavian then won the civil wars, defeating Antony and Cleopatra at Actium in 31 BC [1]. In 27 BC the Senate gave him the title Augustus, which is often seen as the end of the Republic [1]. He took the modest title princeps, meaning "first citizen" [3].
Several things changed:
- Who decided. Two consuls had shared the top job each year. Under Augustus and later emperors, one man controlled the armies and most of the provinces [3].
- The army. Generals once served for a campaign and then returned to civilian life. Under the emperors the legions answered to the ruler.
- The provinces. Some provinces stayed under the Senate, but imperial ones were governed by legates appointed by the emperor [2].
- Succession. Offices in the Republic were filled by election. An emperor's heir was usually a relative or an adopted son.
What did not change is the empire in the broad sense of Rome ruling other peoples. That began under the Republic. See how the empire grew for the sequence, and east and west for what happened later.
An example from our data
Move the slider from 44 BC to AD 14. At the first date the Republic's outline covers about 1.97 million km². At the second, the year Augustus died, the empire covers about 3.67 million km² and holds 36 provinces, against 28 before. Egypt, taken by Augustus, is one of the additions. By AD 117 the total reaches 4.88 million km². Both of the first two outlines are rebuilt from the provinces Rome held, so treat the exact figures as estimates.
Earlier still, at 133 BC, the Republic held 13 provinces. That is why the Republic cannot be called a small city-state with an empire added on later.
The thing people get wrong
The common mistake is to think the Republic ended and the Empire began on a single day, and that the Senate vanished. Neither is true. Augustus claimed to have restored the Republic, and the Senate, consuls and elections carried on under the emperors with far less real power [2]. Historians therefore describe the change as gradual and sometimes disagree about the best date to give it. The other mistake is to believe that "empire" means "emperor". Rome had conquered most of the Mediterranean before it had an emperor at all.
Republic vs Empire at a glance
| Republic | Empire | |
|---|---|---|
| Traditional dates | 509 BC to 27 BC | 27 BC onwards |
| Ruler | Two consuls a year, with the Senate | An emperor |
| Provinces on the map | 28 at 44 BC | 36 at AD 14 |
| Largest outline | 1.97 million km² | 4.88 million km² |
Frequently asked questions
Was Julius Caesar an emperor?
No. He was dictator for life in 44 BC, during the Republic, and was murdered that year. His heir Augustus became the first emperor.
Did Rome have an empire during the Republic?
Yes, in the sense of ruling many other peoples. By 133 BC Rome held 13 provinces. What it did not have was an emperor.
Which was bigger on the map, the Republic or the Empire?
The Empire. Our largest outline is 4.88 million km² in AD 117, against 1.97 million km² for the Republic at 44 BC.
Sources
- Roman Republic, Wikipedia.
- Roman Empire, Wikipedia.
- Principate, Wikipedia.
- Every figure from our own map is worked out from the datasets on the data sources page (checked against Ancient World Mapping Center outlines and Pleiades).