The Gallienus usurpers were the usurpers who claimed imperial power during the reign of Gallienus (253–268, the first part of which he shared with his father Valerian). The existence of usurpers during the Crisis of the Third Century was very common, and the high number of usurpers fought by Gallienus is due to his long rule; 15 years was a long reign by the standards of the 3rd century Roman Empire.