Regalianus was acclaimed emperor by the troops along the Danube river, a region of the empire that frequently experienced barbarian raids, probably in the hope that he might be able to secure the frontier.

Unlike Ingenuus, and revolutionary for an imperial claimant, Regalianus founded his own mint at Carnuntum, his seat of power.

How exactly he met his end is not entirely clear, but the most commonly accepted theory is that he died during a raid of Carnuntum by the Roxolani, possibly aided by a contingent of his men who had grown to oppose him.

The often unreliable Historia Augusta, a late Roman collection of imperial biographies, records that Regalianus was of Dacian origin, and a descendant of Decebalus, the king of Dacia who had been defeated with great effort by emperor Trajan in 105–107.

[4] Charles Theodore Beauvais de Preau believed based on engravings of coins by Hendrick Goltzius that his named was "Quintus Nonius Regillianus" but Joseph Hilarius von Eckhel thought that they instead belonged to some other Princeps and that the coins were the result of ignorant moneyers who failed to make legible coins, John Yonge Akerman noted that the standard of the cross described to be on the mint makes dates them to a later period, his opinion was that this supposed "Nonius" would have been a usurper during the reign of Constantius II.

[4] These provinces along the Danube suffered from frequent barbarian raids, which often left them at odds with the central imperial government.

[4] Shortly prior to Regalianus' own claim to imperial power, the usurper Ingenuus had been proclaimed in the region in 260, but he had quickly been defeated by the reigning emperor, Gallienus (r. 253–268).

[8] After defeating Ingenuus, Gallienus had spent some time reorganising the defenses along the Danube, but had to return to Italy to deal with an invasion by the Alemanni, a Germanic tribe.

It is likely that the legionaries of Legio XIV Gemina, which was stationed at Carnuntum, supported the accession of Regalianus as they hoped he could help secure the Danube border.

[9] In addition to his own portrait, Regalianus' coins also depict his wife, whom he raised to the rank of Augusta to bolster his position.