Didius Julianus (Marcus Didius Salvius Julianus)dĭˈdēəs jōlēāˈnəs, d. 193, Roman emperor (193). He was consul under Pertinax, on whose death the Praetorian Guard received bids for the position of emperor. Didius bid highest and became emperor. Two months later he was murdered when Septimius Severus, who would not recognize him, bought the support of the Praetorian Guard. Severus succeeded him.