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; fifteen years being considered long by the standards of the 3rd century Roman Empire.

After Valerian's defeat and capture by the Persians in 260, his son Gallienus became the only emperor. However, many uprisings happened, both in the East, with the formation of the Palmyrene Empire, and in the West, with the birth of the Gallic Empire. With the uncertainty of the period, the legions wanted to restore Roman power in the wake of Valerian's defeat, against the pressure of the barbarian people in the west and the Persians in the East.

The author(s) of the Historia Augusta listed several other Gallienus usurpers in the book on the "Thirty Tyrants." Given the notorious unreliability of the Historia Augusta, the veracity of this list is debatable. There is a scholarly consensus that the author deliberately inflated the number of pretenders in order to parallel the Thirty Tyrants of Athens. Edward Gibbon identified nineteen. The Historia actually gives 32 names. The author, who wrote under the name of Trebellius Pollio, places the last two during the reigns of Maximinus Thrax and Claudius II respectively, leaving thirty alleged pretenders during the reign of Gallienus.

The following list gives the Thirty Tyrants as depicted by the Historia Augusta, along with notes contrasting the Historia Augusta's claims with their actual historical positions:

Notwithstanding the author's pretensions regarding the time during which these persons aspired to the throne, this list includes:

This leaves nine pretenders roughly contemporary with Gallienus. According to David Magie (the editor of the Loeb Classical Library edition of the Historia Augusta), at least some of these men issued coins.