Princess Enflaeda was the daughter of King Edwin of Northumbria, by his second Wife, St. Ethelburga of Lyming. She was born at Easter AD 626, and baptised at Pentecost by St. Paulinus, her mother's chaplain. On the defeat of her father in AD 633, she shared the flight of her mother and Bishop Paulinus to Kent and was brought up partly at the court of her uncle, King Edbald, and partly at the first nunnery built in England, at Lyming, where her mother was abbess.

Oswiu succeeded his brother, St. Oswald, as King of Bernicia, and by conquest, became King of Deira, the other part of Northumbria. In AD 642, he married the young Enflaeda, who was his maternal cousin. Like his wife, he was a Christian and during his twenty-eight years' reign did so much for the advance of Christianity in his own and the neighbouring kingdoms, despite some inexcusable actions, chief among which was the assassination of his rival, King Oswin of Deira. At the instigation of Enflaeda, and in expiation of the murder of Oswin, Oswiu built a monastery at Gilling, the scene of the tragedy; so that holy men might make constant intercession for the souls of the murdered and the murderer. Enflaeda's piety and good works were well known to the Pope and, in appreciation of her virtues, he sent her a cross made out of the chains of St. Peter and St. Paul, with a gold key to it.

Queen Enflaeda became a friend and patron of St. Wilfred (the Elder), a man very famous in the annals of the early Anglo-Saxon Church. It was through Enflaeda's influence that, as a boy of thirteen, Wilfrid was enabled to become a monk and, five years afterwards, she assisted him in making his first journey to Rome. It was largely because of such continental trips that Wilfred began the Roman versus Celtic Easter calendar debate which divided the English Church in the mid-7th century. To resolve the ensuing arguments, a conference was held, in AD 664, at St. Hilda's monastery at Whitby. It was widely attended by both clergy or laity, all who had a right to vote in national affairs. St. Enflaeda was on the side of St. Wilfrid, the champion of the Roman cause. The result of the conference was a decree, by King Oswiu, that Easter should be everywhere observed according to the Roman calendar.

After King Oswiu's death on a pilgrimage to Rome in AD 670, Enflaeda spent the rest of her life as a nun at Whitby, to where his body was returned. She ruled as Abbess along with her daughter, St. Elflaeda of Whitby. She died on 11th December AD 704 was buried beside her husband.