Ernulf (1040 – 15 March 1124) was a French Benedictine monk who became prior of Christ Church in Canterbury, abbot of Peterborough, and bishop of Rochester in England.

[2][3] Ernulf was made prior by Archbishop Anselm in 1096 and began the expansion of Lanfranc's rebuilt Canterbury Cathedral, taking down the eastern part of the church which Lanfranc had built and erecting a far more magnificent structure.

[4] On 28 September 1114, he was invested as bishop of Rochester by Ralph d'Escures, the archbishop of Canterbury.

[6] At Peterborough and Rochester, Ernulf had the old buildings torn down and erected new dormitories, refectories, chapter houses, etc.

Ernulf is associated with the production of the Textus Roffensis (a large collection of documents relating to the early Church of Rochester which also included the early Kentish law code attributed to King Aethelberht); "Collectanea de rebus eccl.