Pope St. Gregory the Great

Roman prefect turned monk, then pope in a city of plague and Lombard siege. He fed Rome from the Church's estates, sent Augustine to convert the English, wrote the Pastoral Rule that became the bishop's handbook of the Middle Ages, the Dialogues with the Life of St. Benedict, and the Moralia on Job, a vast exposition of the moral and mystical senses. He reformed the Roman liturgy and chant that bear his name, and refused the title “universal bishop” while exercising the Petrine office in full.

Why he matters: He is the bridge from the Fathers to the Middle Ages: the doctrine of purgatory, the Gregorian Masses, the theology of compunction and contemplation in the active life, and the pastoral ideal of the Church all pass through him. The East honors his Liturgy of the Presanctified.