Publius Helvius Pertinax (1 August 126 – 28 March 193) was Roman emperor for the first three months of 193, succeeding Commodus and becoming the first ruler of the turbulent Year of the Five Emperors.
The son of a freedman, Pertinax rose from modest origins through a military career. He distinguished himself in the Roman–Parthian War of 161–166 and went on to hold a succession of governorships and senior commands. He also sat in the Roman Senate, where he was a contemporary of the historian Cassius Dio.
After the assassination of Commodus, Pertinax was chosen emperor. He aimed at restoring army discipline and imperial financial stability, but his reforms angered the Praetorian Guard, who killed him after just 87 days.