Dionysius the Great (Ancient Greek: Διονύσιος Ἀλεξανδρείας) was the 14th Pope and Patriarch of Alexandria from 28 December 248 until his death on 22 March 264.

[4] During 249, a major persecution was carried out in Alexandria by a polytheist mob, and hundreds of Christians were assaulted, stoned, burned or cut down on account of their refusal to deny their faith.

Many fled from the city into the desert, where most succumbed to exposure, hunger, thirst, or attacks by bandits or wild animals.

Dionysius spent three days in hiding before departing with his servants and other loyal brethren on the fourth night of the Decian decree.

In opposition to Novatian's teaching, Dionysius ordered that the Eucharist should be refused to no one who asked it at the hour of death, even those who had previously lapsed.

Gallienus wrote a letter to Dionysius and other bishops, ensuring their safety and ability to reopen their churches.

That correspondence is cited by Pope Pius IX in his encyclical Praedecessores Nostros (On Aid For Ireland) of 25 March 1847.