Hereswith was one of the sainted daughters of Prince Hereric - nephew of the exiled King Edwin of Deira - and his wife, Bregswith. Her sister was St. Hilda, Abbess of Hartlepool & Whitby. Hereswith was probably born at the Royal Court of Campoduno (near Doncaster) in Elmet, where her unfortunate father was poisoned in AD 616. Shortly afterwards, however, the family was restored to their rightful position in Deira and it is generally supposed that she was amongst King Edwin's relations christened by St. Paulinus at York in AD 627. Both the young princesses, being at an impressionable age, could not fail to have also been influenced by the beauty and charm of their grand-aunt, Queen Ethelburga, who had brought with her, from Kent, a semi-Frankish and Roman degree of refinement, culture and education, somewhat in advance of the rough north-country usages.

Hereswith married Aethelhere, King of East Anglia, and became the mother of the future Kings Aeldwulf and Aelfwold, and probably also St. Jurmin, who was killed fighting against the heathen Mercians and thus honoured as a martyr.

Hereswith eventually desired to take the veil but, in England the first nunnery had only been founded a few years before, in AD 633. There were already many nunneries in France, however, and she had heard much of the holiness of women devoted to the service of God there. Three French houses in particular were much resorted to by English ladies who had the vocation. These were Brie - still under its first abbess, St. Fara - Chelles and Andelys, founded by St. Clothilda. Hereswith took the veil at Chelles, near Paris, then a small building and community but, soon after and probably during the residence there of Hereswith, it was magnificently refounded and endowed by St. Bathilda, Queen of France. St. Hereswith died on 23rd September AD 647.