Roman Emperor from 260 to 268, and for seven years (253-260) associated in the government with his father, the Emperor Valerian; under his lax rule the empire was subjected to hostile inroads on all sides, while in the provinces a succession of usurpers, known as the Thirty Tyrants, sprang up, disowning allegiance, and aspiring to the title of Caesar; in his later years he roused himself to vigorous resistance, but in 268 was murdered by his own soldiers whilst pressing the rebel Aureolus at the siege of Milan.