Commodus becomes sole emperor of the Roman Empire at the age of eighteen, following the death of his father, Marcus Aurelius.

Commodus was Roman emperor from 177 to 192, first serving as nominal co-emperor under his father Marcus Aurelius and then ruling alone from 180. Commodus's sole reign is commonly thought to mark the end of the Pax Romana, a golden age of peace and prosperity in the history of the Roman Empire.

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The term emperor is a modern convention, and did not exist as such during the Empire. When a given Roman is described as becoming emperor in English, it generally reflects his accession as augustus, and later as basileus. Another title used was imperator, originally a military honorific, and caesar, originally a cognomen. Early emperors also used the title princeps alongside other Republican titles, notably consul and pontifex maximus.

The Roman Empire ruled the Mediterranean and much of Europe, Western Asia and North Africa. The Romans conquered most of this during the Republic, and it was ruled by emperors following Octavian's assumption of effective sole rule in 27 BC. The western empire collapsed in 476 AD, but the eastern empire lasted until the fall of Constantinople in 1453.

Marcus Aurelius Antoninus was Roman emperor from 161 to 180 and a Stoic philosopher. He was a member of the Nerva–Antonine dynasty, the last of the rulers later known as the Five Good Emperors and the last emperor of the Pax Romana, an age of relative peace, calm, and stability for the Roman Empire lasting from 27 BC to 180 AD. He served as Roman consul in 140, 145, and 161.