Year of the Six Emperors (238)
Reign of Gordian III (238–244)
Reign of Philip the Arab (244–249)
Reign of Trebonianus Gallus (251–253)
Reign of Aemilianus (253)
Reign of Gallienus (260–268)
Reign of Victorinus (269–271)
Reign of Aurelian (270–275)
P. C(assius?) Regalianus (died 260) was a Dacian general who turned against the Roman Empire and became himself emperor for a brief period, being murdered by the hands who raised him to power.
The main source of information is the unreliable and for the most part fabricated Historia Augusta. Other sources are Eutropius, who calls him Trebellianus, and Aurelius Victor and the Epitome de Caesaribus, which call him Regillianus. About his origin, the Tyranni Triginta says he was a Dacian, a kinsman of Decebalus. He probably was of senatorial rank, and had received military promotion from the Emperor Valerian.
After the defeat and capture of Valerian in the east (260), the border populations felt insecure, and elected their own emperors to guarantee they would have leaders against the foreign threats. The population and the army of the province of Pannonia had chosen Ingenuus, and elected him emperor, but the lawful emperor, Gallienus, had defeated the usurper.
Gallienus had moved to Italia, however, to deal with an invasion of the Alamanni. The local population, facing the threat of the Sarmatians, elected Regalianus emperor, who raised his wife, Sulpicia Dryantilla, who was of noble lineage, to the rank of Augusta to strengthen his position. Regalianus bravely fought thereafter against the Sarmatians. Short time after his victory, he was killed by a coalition of his own people and of the Roxolani.
A few, probably fictitious, anecdotes survive about this man, in the brief biographical sketch of him given in the Book on Thirty Tyrants in the Historia Augusta: it is stated for example that he was raised to the throne because of his name (Regalianus, "of a king" or "kingly"); when his soldiers heard this jest they greeted Regalianus as their emperor.
Media related to Regalianus at Wikimedia Commons