Commodus  31 August 161 – 31 December 192) was a Roman emperor who ruled from 177 to 192. He served jointly with his father Marcus Aurelius from 177 until the latter's death in 180, and thereafter he reigned alone until his assassination. His reign is commonly thought to mark the end of a golden age of peace and prosperity in the history of the Roman Empire (the Pax Romana).

Commodus accompanied his father during the Marcomannic Wars in 172 and on a tour of the Eastern provinces in 176. The following year, he became the youngest emperor and consul up to that point, at the age of 16. His solo reign saw less military conflict than that of Marcus Aurelius, but internal intrigues and conspiracies abounded, goading Commodus to an increasingly dictatorial style of leadership. This culminated in his creating a deific personality cult, including his performances as a gladiator in the Colosseum. Throughout his reign, Commodus entrusted the management of affairs to his palace chamberlain and praetorian prefects, namely Saoterus, Perennis and Cleander.

His brutal misrule precipitated civil strife that ended 84 years of stability and prosperity within the empire. 

Soon after he became sole ruler, Lucius changed his name to Marcus Aurelius Commodus Antoninus. In 182 Commodus’s sister Lucilla conspired with a group of senators to assassinate him. The plot failed, and Commodus retaliated by executing a number of leading senators. Thereafter his rule became increasingly arbitrary and vicious. In 186 he had his chief minister executed in order to appease the army; three years later he allowed the minister’s successor to be killed by a rioting crowd. Political influence then passed to the emperor’s mistress and two advisers.

 Meanwhile, Commodus was lapsing into insanity. He gave Rome a new name, Colonia Commodiana (Colony of Commodus), and imagined that he was the god Hercules, entering the arena to fight as a gladiator or to kill lions with bow and arrow. On December 31, 192, his advisers had him strangled by a champion wrestler, following his announcement the day before that he would assume the consulship, dressed as a gladiator. A grateful Senate proclaimed a new emperor—the city prefect, Publius Helvius Pertinax—but the empire quickly slipped into civil war. 

Commodus' assassination in 192, by a wrestler in the bath who held him underwater, marked the end of the Nerva–Antonine dynasty. He was succeeded by Pertinax, the first claimant in the tumultuous Year of the Five Emperors.