Æthelburg was one of the daughters of King Anna of East Anglia although she was probably illegitimate. Her sisters were Saint Withburga, Saint Saethrid, who was abbess of Faremoutiers Abbey in Brie, Saint Seaxburh and Æthelthryth who were abbesses of Ely.
Æthelburg and Saethrid were sent to the nunnery of Faremoutiers for their education. While there Æthelburg became a nun and eventually succeeded Saethrid as abbess. As abbess, Æthelburg began work on a church in honour of the twelve apostles which was left unfinished at her death in 664. At her request she was buried in the church. After seven years a decision was made to move her bones to the near-by church of Saint Stephen and her body was found to be uncorrupted.