This is a translation into English of the letters of Arnulf of Lisieux. Arnulf was involved with many major events of the 12th century: his correspondents included kings, popes, cardinals, fellow bishops, abbots, scholars and friends. Arnulf began his career in the midst of the English civil war between King Stephen and the Empress Matilda. He worked closely with Bernard of Clairvaux, accompanied Louis VII and Eleanor of Aquitaine on the Second Crusade, and was an early advocate of young Duke Henry of Normandy in his campaign to become Henry II of England, and later served Henry's court in several capacities. His actions in the Beckett controversy led to the final settlement which brought Henry to his knees at the altar of Canterbury. This version of his letters seeks to capture the author's allusions, implications and rhetorical style. It identifies many personal and place names, and traces quotes and paraphrasing which Arnulf borrowed from the Vulgate Bible, classical treatises and the works of his contemporaries.Based on 19 extant manuscripts, it restores the letters to their original order, and draws some conclusions about the author's intent in compiling and preserving the collection.