Being a Roman emperor was a risky job. It wasn’t unusual for emperors to be killed by usurpers wanting to remove them from power. They also faced many health challenges,such as death from epidemics and infections.

Despite the hazards, some emperors managed to achieve long reigns. But which Roman emperor ruled the longest?

“On one level it’s pretty basic, as you can just look at a list of emperors and see who had the longest reign,” David Parnell, a history professor at Indiana University Northwest, told Live Science in an email. However, the question is actually trickier than it seems.

first of all, you have to define when exactly the Roman Empire ended. The Roman Empire

One strong contender for the title of longest-reigning emperor is Augustus. He gained prominence when his great uncle Julius Caesar named him his successor in his will. After the assassination of Julius Caesar in 44 B.C., Octavian formed a triumvirate ruling with Mark antony and a statesman named lepidus.

a statue of the Roman emperor Augustus

augustus might be considered the longest-ruling Roman emperor by some definitions. (Image credit: Gilmanshin via Shutterstock)

Lepidus was removed from power in 36 B.C. and a civil war erupted between Octavian and Mark antony that led to Antony’s defeat and suicide in 30 B.C. Cleopatra VII, the pharaoh of Egypt who had children with Antony and Julius Caesar, died by suicide that same year. But Cleopatra and Caesar’s heir – the child Caesarion – was still alive.Not wanting to take chances,Octavian had him killed to prevent him from being a threat to his rule.

In 27 B.C., the Roman senate gave Octavian the title “Augustus” (meaning “revered one” in Latin).

During his rule, Augustus repaired, refurbished and rebuilt a vast array of buildings and infrastructure in Rome, including temples, shrines, the forum, the senate house, sewers and roads, Diane Favro, a professor emerita of architecture and urban design at UCLA, wrote in a chapter of the book “The Cambridge Companion to the Age of Augustus” (Cambridge University Press, 2005). Civil wars during the first century B.C. meant that Rome’s infrastructure had been neglected and was badly in need of refurbishment, Favro noted.

Though, Augustus’ rule also suffered defeats. During his reign, Augustus also tried to expand the Roman Empire into Germany. This ended in disaster with three Roman legions being annihilated at the Battle of the Teutoburg Forest in A.D. 9.

The ancient writer Suetonius (lived circa 69 to 122) claimed that after augustus heard the news, he refused to cut his beard or hair for several months. He also wrote that at times, Augustus would bang his head against a door and call for Quinctilius Varus (the commander of the legions who was killed in the battle) to “give me back my legions!” (translation by J. C.Rolfe)

Roman emperor quiz: Test your knowledge on the rulers of the ancient empire