Ernulf was a French Benedictine monk who became prior of Christ Church in Canterbury, abbot of Peterborough, and bishop of Rochester in England. A jurist and an architect as well, he was responsible for greatly expanding Canterbury Cathedral during his time there.

Canterbury Cathedral, more correctly Christ Church Cathedral, Canterbury, is the cathedral of the archbishop of Canterbury, the leader of the Church of England and symbolic leader of the worldwide Anglican Communion. Located in Canterbury, Kent, it is one of the oldest Christian structures in England and forms part of a World Heritage Site. Its formal title is the Cathedral and Metropolitical Church of Christ, Canterbury.