Donatus comes from a Deo natus, born of God, that is, by regeneration and the infusion of grace and glorification, which are a threefold spiritual rebirth through God. For when the saints die they are said to be born, whence the day of a saint's death is called his natal feast. A child in sooth strains to be born, in order that he may have more room to move, more abundant food to eat, a freer air to breathe, and light to see. And since the saints, by death, issue from the womb of their mother the Church, they receive these four things according to their mode, and thus are said to be born. Or again, Donatus is the same as dono datus, he who is given.

Donatus was reared and instructed with the Emperor Julian, at the time when Julian was ordained a subdeacon. But as soon as Julian was raised to the rank of emperor, he put the father and mother of Donatus to death. Donatus himself fled to Arezzo where he dwelt with the monk Hilary, and wrought many miracles. One day the prefect of the city brought his son to him, the boy being possessed of the Devil. The unclean spirit within him cried out: 'In the name of the Lord Jesus Christ, Donatus, molest me not, nor drive me forth from my house! O Donatus, why do you torment me?' But Donatus prayed, and at once the prefect's son was delivered.

A tax-gatherer in Tuscany, named Eustacllius, left the public monies in the care of his wife Euphrosina, who, seeing the province overrun by enemies, hid the monies and then died, overcome with grief. When her husband returned, he was unable to find the treasure, and was about to be handed over with his sons to the executioners, when he had recourse to Saint Donatus. The saint went with him to Euphrosina's tomb, and having prayed, said in a loud voice: 'Euphrosina, I adjure you by the Holy Ghost, tell us where you have placed the monies!' And at once a voice from the tomb said: 'I buried all under the doorsill of my house!' And going thither, they found the money, as she had said.

Some days later the bishop Satyrus expired in the Lord, and the clergy elected Donatus in his place. And one day, as Gregory relates in his Dialogue, the people were receiving the Holy Communion in the Mass, and the deacon was distributing the Blood of Christ, when the pagans pushed him so rudely that he fell, and the holy chalice was shattered. As he and the people were sore aggrieved at that, Donatus gathered the fragments of the chalice, and having prayed, restored it to its former shape. The Devil, however, hid one fragment, and this is still lacking in the chalice, as a testimony of the miracle. And at the sight of this miracle, eighty pagans were converted and received baptism.

Near Arezzo there was a poisoned spring, and anyone who drank thereof died immediately. And when Saint Donatus rode upon his donkey to the spring in order to purify the waters by his prayers, a terrible dragon rushed forth, twisted his tail about the donkey's legs, and reared up against Donatus. But the saint struck him with a whip, or, as others have it, spat in his face, and killed him in a trice. Then he besought the Lord, and the waters of the spring were purified forthwith. Another time, when he and his companions were suffering from thirst, he prayed, and caused a spring to break forth at the spot where they stood.

The daughter of the Emperor Theodosius, being possessed of the Devil, was brought to Saint Donatus, who said: 'Begone, unclean spirit, and dwell not in this body fashioned by God!' And the demon answered: 'Tell me how I shall go out, and whither I shall go!' 'Whence are you come?' asked the saint. 'From the desert!' answered the demon. 'Go back to the desert!' said the saint. And the demon replied: 'I see on you the sign of the cross, whence a fire leaps out against me, and for the fear I have I know not whither to go. But give me room to pass, and I shall go out!' And Donatus said: 'There, you have room to pass: go back to your place!' And the demon went out, making the whole house to quake as he passed.

A dead man was borne on his way to the tomb, when a man came up, holding a document in his hand, and declared that the defunct owed him two hundred solidi, and that he would not allow him to be buried until the sum was paid. The dead man's wife went in tears to tell this to Saint Donatus, affirming at the same time that the man had already received payment of all the money. Then the saint betook himself to the bier, and taking the dead man by the hand, said to him: 'List to me!' And the defunct responded: 'I hear!' 'Arise,' said Saint Donatus, 'and deal with this man who forbids you to be buried!' The dead man sat up, proved before all that he had acquitted the debt, took the writing and tore it in pieces. Then he said to Saint Donatus: 'Father, bid me sleep again!' And the saint answered: 'My son, go now to your rest!'

At that time no rain had fallen for almost three years, and a great barrenness lay upon the land. The infidels therefore went to the Emperor Theodosius, and demanded that Donatus be delivered to them, for that he had caused the drought by his magical arts. At the emperor's urging Donatus came out, prayed to the Lord, and thus brought down an instant fall of rain. Then he went back to his house, his garments being dry, although the others were drenched with rain.

Some time thereafter, when the Goths were ravaging Italy, and many were renouncing the faith of Christ, Saint Donatus and Saint Hilary went to the prefect Quadracianus, and rebuked him for his apostasy. At this the prefect seized the two saints, and commanded them to sacrifice to Jupiter. And when they refused, Hilary was stripped and beaten until he breathed forth his soul, and Donatus was imprisoned, and then beheaded. The martyrdom took place in Arezzo about the year of the Lord 380.