Olympias was born about the year 361 into one of the chief families of the Eastern capital. Her grandfather had been Praetorian Prefect under Constantine; her father, of the senatorial rank; and she was an only child, sole heiress to a fortune so great that Palladius could not name it without remarking that it exceeded what was decent to write down. Orphaned in early youth, she was committed to the guardianship of a kinswoman, Theodosia, sister of Saint Amphilochius of Iconium, a woman of strict piety, in whose household the girl was reared as the Fathers reared their own daughters: in the Scriptures, in continence, and in the works of mercy.

From her youth she stood already within the circle of the saints. Saint Gregory the Theologian counted her among his correspondents, and one of his letters preserved in the collection (the twenty-fourth) is addressed to her with the affection of an old man writing to a daughter in the faith. She was therefore not a convert raised up out of the world by an exceptional grace, but a soul prepared from childhood for the gift she would receive.

Sometime about her eighteenth year she was given in marriage to Nebridius, prefect of the city, a man of senatorial rank and of irreproachable life. The marriage lasted a very little while — the Vita reckons it at twenty months, Palladius simply at less than two years — for Nebridius died, leaving Olympias a widow before she had borne a child. So sudden a bereavement, in a fortune so great and a woman so young, drew the notice of the imperial house at once.

The emperor Theodosius wrote to her urging her to marry one of his own kinsmen, a Spaniard named Elpidius. She returned the answer that if God had wished her to remain in the married state He would not have taken her first husband from her so soon, and that for her part she would now be only the bride of Christ. The emperor, displeased, did what an emperor displeased could do: he placed her whole patrimony under the guardianship of the prefect of the city, with orders that she was not to touch any of it until she had reached her thirtieth year.

Olympias received the imperial restriction without protest. She wrote to the emperor in turn that she was grateful to him, for he had relieved her of the burden of administering a fortune, which was a heavier burden than the loss of it; she begged only that he would give the remainder of it to the bishops and to the poor, so that she might be free of it altogether. The emperor, in whose household the answer was read aloud, recognised that he had been overmatched, and ordered the guardianship lifted and the property restored in full.

When the property was returned to her, she did what she had asked the emperor to do for her. She poured it out in alms; she ransomed captives from across the empire; she endowed hospitals and almshouses for women, and the houses for the poor and the strangers attached to the cathedral church; she paid the debts of poor clergy and the expenses of bishops travelling on the business of the Church; and she sent money to monasteries in Egypt, in Palestine, and in Mesopotamia, by the hand of trusted messengers. Palladius records the names of bishops and ascetics who received support from her: among them were Saint Amphilochius of Iconium, Saint Optimus of Antioch in Pisidia, Saint Peter of Sebaste, Saint Epiphanius of Salamis, and many others. She gave, the Vita says, until the rumour ran in the city that no almsgiving had ever been seen like hers since the days of the apostles.

The Patriarch Nectarius, judging that she had been tested and proved, ordained her deaconess of the Great Church of Constantinople when she had reached, or was very near, her thirtieth year. With three of her widowed kinswomen — Elisanthia, Martyria, and Palladia — she founded a community of consecrated women on the ground adjoining the Cathedral of Hagia Sophia, on the south side, where they lived in common, in fasting and in psalmody, and in the works of the diaconate as the canons set them out: instruction of the catechumens, attendance on the women at baptism, ministry to the sick, and the daily distribution to the poor at the gate of the church.

When Saint John Chrysostom came up from Antioch to the see of Constantinople, in the year 398, he found in her the daughter that one ascetic finds in another. He took the community of Olympias under his immediate care; he preached for them in their oratory; and through her hand many of his charities to the city were administered. Palladius, who knew them both, says that Saint John loved Olympias as a man loves his own soul, and trusted her judgement in the management of the church's almsgiving above that of any of his clergy.

When the Synod of the Oak deposed Saint John, and the empress Eudoxia drove him from the city, Olympias did not waver. She continued to send him food, money, and clothing in his exile; she received the bishops who remained loyal to him when they could no longer be received elsewhere; she paid the fines and the bribes by which his other supporters were freed from prison. For this she was summoned before the new patriarch Arsacius, then before the prefect of the city, then before Atticus who came after; she was charged with refusing to communicate with the bishops in possession; she was fined heavily and at last was banished from Constantinople, with the order that she withdraw to Nicomedia and remain there.

From his own exile, first at Cucusus in the Taurus and then on the road to Pityus on the Black Sea, Saint John wrote her seventeen letters that have come down to us, comforting her in her afflictions of body and soul. They are letters of a confessor to a confessor, full of his characteristic tenderness; he tells her not to be cast down, that the only true evil is sin, and that she who suffers for righteousness suffers what the saints have always suffered.

Olympias died at Nicomedia, worn out by sickness and grief, about the year 408 — some chronographers reckon 410. Her relics, which her community had taken with them into exile and kept, were translated back to Constantinople in the time of Bishop Pansophius of Nicomedia, by an apparition of the saint herself directing the place of their reception, and were enshrined in the church of Saint Thomas at the Embolus of Domninus, where they remained the centre of a popular veneration until the fall of the city. The Church honours her on the twenty-fifth of July, as a deaconess of the Great Church and a confessor of Saint John Chrysostom.