Pope Gregory I (Latin: Gregorius I; c. 540 – 12 March 604), commonly known as Saint Gregory the Great, was Bishop of Rome from 3 September 590 to his death. He is known for instigating the first recorded large-scale mission from Rome, the Gregorian Mission, to convert the then largely pagan Anglo-Saxons to Christianity. Gregory is also well known for his writings, which were more prolific than those of any of his predecessors as pope. The epithet Saint Gregory the Dialogist has been attached to him in Eastern Christianity because of his Dialogues. English translations of Eastern texts sometimes list him as Gregory "Dialogos", or the Anglo-Latinate equivalent "Dialogus".A Roman senator's son and himself the prefect of Rome at 30, Gregory lived in a monastery he established on his family estate before becoming a papal ambassador and then pope. Although he was the first pope from a monastic background, his prior political experiences may have helped him to be a talented administrator. During his papacy, his administration greatly surpassed that of the emperors in improving the welfare of the people of Rome, and he challenged the theological views of Patriarch Eutychius of Constantinople before the emperor Tiberius II. Gregory regained papal authority in Spain and France and sent missionaries to England, including Augustine of Canterbury and Paulinus of York. The realignment of barbarian allegiance to Rome from their Arian Christian alliances shaped medieval Europe. Gregory saw Franks, Lombards, and Visigoths align with Rome in religion. He also combated the Donatist heresy, popular particularly in North Africa at the time.Throughout the Middle Ages, he was known as "the Father of Christian Worship" because of his exceptional efforts in revising the Roman worship of his day. His contributions to the development of the Divine Liturgy of the Presanctified Gifts, still in use in the Byzantine Rite, were so significant that he is generally recognized as its de facto author.

Gregory is one of the Latin Fathers and a Doctor of the Church. He is considered a saint in the Catholic Church, Eastern Orthodox Church, Anglican Communion, various Lutheran denominations, and other Protestant denominations. Immediately after his death, Gregory was canonized by popular acclaim. The Protestant reformer John Calvin admired Gregory greatly and declared in his Institutes that Gregory was the last good Pope. He is the patron saint of musicians, singers, students, and teachers.