Mildthryth was the daughter of King Merewalh of Magonsaete, a sub-kingdom of Mercia, and Eormenburh (Saint Eormenburga), herself the daughter of King Æthelberht of Kent, and as such appearing in the so-called Kentish royal legend.
Her sisters Milburh (Saint Milburga of Much Wenlock) and Mildgytha (Saint Mildgyth) were also considered saints. Goscelin, probably relying on a now-lost history of the rulers of the Kingdom of Kent, wrote a hagiography of Mildthryth.
Mildthryth's maternal family had close ties to the Merovingian rulers of Gaul, and Mildthryth is said to have been educated at the prestigious Merovingian royal abbey of Chelles. She entered the abbey of Minster-in-Thanet, which her mother had earlier established, and of which she became abbess by 694. Suggesting that ties to Gaul were maintained, a number of dedications to Mildthryth exist in the Pas-de-Calais, including at Millam. Mildthryth died at Minster-in-Thanet and was buried there.
Her remains were translated to St Augustine's Abbey, Canterbury in 1030, an event commemorated on 18 May. Mildthryth was apparently followed as abbess by Edburga of Minster-in-Thanet, correspondent of Saint Boniface.
- Brooks, Beda: The world of Saint Mildred, c. 660- 730. A study of an Anglo-Saxon nun in the golden age of the English Church, Bath 1996, ISBN 1-898663-08-4.
- Rollason, David W.: The Mildrith legend. A study in early Medieval hagiography in England, Leicester 1982, ISBN 0-7185-1201-4.
- Love, R. C., "Mildrith, St" in Michael Lapidge et al., The Blackwell Encyclopedia of Anglo-Saxon England. Oxford: Blackwell, 1999. ISBN 0-631-22492-0
- Rollason, D. W., The Mildrith Legend: a study in early medieval hagiography in England (series "Studies in the Early History of Britain", Leicester University Press) 1983.
- Primary texts in Old English and translation, with further information
- O.S.B., "Saint Mildred andher Kinsfolk", Virgin Saints of the Benedictine Order, Catholic Truth Society, London, 1903