The Roman Empire was ruled by emperors starting with Augustus, who became the first emperor in 27 BCE after being granted the title by the Roman Senate. He established the imperial system that limited the Senate's power and centralized authority under the emperor
. Notable emperors during the empire's history include:
- Augustus (27 BCE–14 CE), the founder of the empire
- Tiberius (14–37 CE)
- Caligula (37–41 CE)
- Nero (54–68 CE)
- Trajan (98–117 CE)
- Marcus Aurelius (161–180 CE)
- Diocletian (284–305 CE), who reformed the empire's governance by splitting it into Eastern and Western halves, each ruled by an augustus (senior emperor) and supported by a caesar (junior emperor), creating the Tetrarchy system
After Diocletian's reforms, the empire was effectively ruled by multiple emperors simultaneously to manage its vast territories. The Western Roman Empire and Eastern Roman Empire (later Byzantine Empire) had separate emperors from 286 CE onward
. The last emperor of the Western Roman Empire was Romulus Augustulus, who ruled until 476 CE, marking the traditional end of the Western Empire
. The Eastern Roman Empire continued with its own line of emperors for nearly a thousand more years. In summary, the Roman Empire was ruled by a succession of emperors starting with Augustus in 27 BCE, evolving through various dynasties and administrative reforms, including the Tetrarchy under Diocletian, until the fall of the Western Empire in 476 CE.
