Pope Gregory I (; ; – 12 March 604), commonly known as Saint Gregory the Great (; ), was the 64th Bishop of Rome from 3 September 590 until his death on 12 March 604.

Gregory was originally from Rome, a Roman senator's son, and himself the prefect of Rome at 30. He lived in a monastery that he established on his family estate before becoming a papal ambassador and then pope. During his papacy, his administration greatly surpassed that of the emperors Maurice and Theodosius in improving the welfare of the people of Rome. Gregory regained papal authority in Spain and France and sent missionaries to England, including Augustine of Canterbury and Paulinus of York. Gregory saw Franks, Lombards, and Visigoths align with Rome in religion from their Arian Christian alliances. The realignment of barbarian allegiance to Rome shaped medieval Europe. He also combated the Donatist heresy, popular particularly in North Africa at the time.

Gregory is also well known for his writings, which were more prolific than those of any of the previous popes.Ekonomou, 2007, p. 22. The epithet Saint Gregory the Dialogist has been attached to him in Eastern Christianity because of his Dialogues. 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 honored, along with Augustine, Jerome and Ambrose, as one of the four Great Latin Church Fathers. Immediately after his death, Gregory was canonized by popular acclaim. He is the second of the three Popes listed in the Annuario Pontificio with the title "the Great", alongside Popes Leo I and Nicholas I.

Early life Gregory was born in Rome, at that time recently reconquered by the Eastern Roman Empire from the Ostrogoths. His parents named him Gregorius, which according to Ælfric of Eynsham in An Homily on the Birth-Day of S. Gregory, "is a Greek Name, which signifies in the Latin Tongue, Vigilantius, that is in English, Watchful". The medieval writer who provided this etymology did not hesitate to apply it to the life of Gregory. Ælfric states, "He was very diligent in God's Commandments."

Gregory was born into a wealthy noble Roman family with close connections to the church. His father, Gordianus, a patrician who served as a senator and for a time was the Prefect of the City of Rome,Thornton, pp 163–8 also held the position of Regionarius in the church, though nothing further is known about that position. Gregory's mother, Silvia, was well-born, and had a married sister, Pateria, in Sicily. His mother and two paternal aunts, Trasilla and Emiliana, are honored by Catholic and Orthodox churches as saints. Gregory's great-great-grandfather had been Pope Felix III.Dudden (1905), page 4. Gregory's election to the throne of St. Peter made his family the most distinguished clerical dynasty of the period.

The family owned and resided in a villa suburbana on the Clivus Scauri on the Caelian Hill, (now the Via di San Gregorio). It branched from the road having the former palaces of the Roman emperors on the Palatine Hill opposite. The north of the street runs into the Colosseum; the south, the Circus Maximus. In Gregory's day, the ancient buildings were in ruins and were privately owned.Dudden (1905), pages 11–15. Villas covered the area. Gregory's family also owned working estates in SicilyDudden (1905), pages 106–107. and around Rome. Gregory later had portraits of his parents frescoed in their former home on the Caelian and these were described 300 years later by John the Deacon. Gordianus was tall with a long face and light eyes. He wore a beard. Silvia was tall, had a round face, blue eyes and a cheerful look. They had another son whose name and fate are unknown.Dudden (1905), pages 7–8.

Gregory was born into a period of upheaval in Italy. From 542 the Plague of Justinian swept through the provinces of the empire, including Italy. The plague caused famine, panic, and sometimes rioting. In some parts of the country, over a third of the population was wiped out or destroyed, with heavy spiritual and emotional effects on the people of the empire. Politically, although the Western Roman Empire had long since vanished in favor of the Gothic kings of Italy, during the 540s Italy was gradually retaken from the Goths by Justinian I, emperor of the Eastern Roman Empire ruling from Constantinople. As the fighting was mainly in the north, the young Gregory probably saw little of it. Rome was sacked and vacated by Totila in 546, destroying most of its population, but in 549 he invited those who were still alive to return to the empty and ruined streets. It has been hypothesized that young Gregory and his parents retired during that intermission to their Sicilian estates, to return in 549.Dudden (1905), pages 36–37. The war was over in Rome by 552, and a subsequent invasion of the Franks was defeated in 554.

Like most young men of his position in Roman society, Gregory was well educated, learning grammar, rhetoric, the sciences, literature, and law; he excelled in all these fields. Gregory of Tours reported that "in grammar, dialectic and rhetoric ... he was second to none". He wrote correct Latin, but his claim not to have known Greek seems to be an exaggeration given his excellent education and time spent in Constantinople. His first language was Piedmontese. He knew Latin authors, natural science, history, mathematics, and music and had such a "fluency with imperial law" that he may have trained in it "as a preparation for a career in public life". He became a government official, advancing quickly in rank to become, like his father, Prefect of Rome, the highest civil office in the city, when only thirty-three years old.

The monks of the Monastery of St. Andrew, established by Gregory at the ancestral home on the Caelian, had a portrait of him made after his death, which John the Deacon also saw in the 9th century. He reports the picture of a man who was "rather bald" and had a "tawny" beard like his father's and a face that was intermediate in shape between his mother's and father's. The hair that he had on the sides was long and carefully curled. His nose was "thin and straight" and "slightly aquiline". "His forehead was high." He had thick, "subdivided" lips and a chin "of a comely prominence" and "beautiful hands".

In the modern era, Gregory is often depicted as a man at the border, poised between the Roman and Germanic worlds, between East and West, and above all, perhaps, between the ancient and medieval epochs.Leyser pg 132

Monastic years

On his father's death, Gregory converted his family villa into a monastery dedicated to Andrew the Apostle (after his death, it was rededicated as San Gregorio Magno al Celio). In his life of contemplation, Gregory concluded that "in that silence of the heart, while we keep watch within through contemplation, we are as if asleep to all things that are without."Cavadini pg 155

Gregory had a deep respect for the monastic life and particularly the vow of poverty. Thus, when it came to light that a monk lying on his deathbed had stolen three gold pieces, Gregory, as a remedial punishment, forced the monk to die alone, then threw his body and coins on a manure heap to rot with a condemnation, "Take your money with you to perdition." Gregory believed that punishment for sins can begin, even in this life before death.Straw pg 47 However, in time, after the monk's death, Gregory had 30 Masses offered for the man to assist his soul before the final judgment. He viewed being a monk as the "ardent quest for the vision of our Creator." His three paternal aunts were nuns renowned for their sanctity. However, after the eldest two, Trasilla and Emiliana, died after seeing a vision of their ancestor Pope Felix III, the youngest soon abandoned the religious life and married the steward of her estate. Gregory's response to this family scandal was that "many are called, but few are chosen." Gregory's mother is herself a saint.

Eventually, Pope Pelagius II ordained Gregory a deacon and solicited his help in trying to heal the schism of the Three Chapters in northern Italy. However, this schism was not healed until well after Gregory was gone.

Apocrisiariate (579–585)

In 579, Pelagius II chose Gregory as his apocrisiarius (ambassador to the imperial court in Constantinople), a post Gregory would hold until 586.Ekonomou, 2007, p. 8. Gregory was part of the Roman delegation (both lay and clerical) that arrived in Constantinople in 578 to ask the emperor for military aid against the Lombards.Ekonomou, 2007, p. 9. With the Byzantine military focused on the East, these entreaties proved unsuccessful; in 584, Pelagius II wrote to Gregory as apocrisiarius, detailing the hardships that Rome was experiencing under the Lombards and asking him to ask Emperor Maurice to send a relief force. Maurice, however, had long ago determined to limit his efforts against the Lombards to intrigue and diplomacy, pitting the Franks against them. It soon became obvious to Gregory that the Byzantine emperors were unlikely to send such a force, given their more immediate difficulties with the Persians in the East and the Avars and Slavs to the North.Ekonomou, 2007, p. 10.

Controversy with Eutychius

According to Ekonomou, "if Gregory's principal task was to plead Rome's cause before the emperor, there seems to have been little left for him to do once imperial policy toward Italy became evident. Papal representatives who pressed their claims with excessive vigor could quickly become a nuisance and find themselves excluded from the imperial presence altogether". Gregory had already drawn an imperial rebuke for his lengthy canonical writings on the subject of the legitimacy of John III Scholasticus, who had occupied the Patriarchate of Constantinople for twelve years prior to the return of Eutychius (who had been driven out by Justinian). Gregory turned to cultivating connections with the Byzantine elite of the city, where he became extremely popular with the city's upper class, "especially aristocratic women". Ekonomou surmises that "while Gregory may have become spiritual father to a large and important segment of Constantinople's aristocracy, this relationship did not significantly advance the interests of Rome before the emperor". Although the writings of John the Deacon claim that Gregory "labored diligently for the relief of Italy", there is no evidence that his tenure accomplished much towards any of the objectives of Pelagius II.Ekonomou, 2007, pp. 10–11.

In Constantinople, Gregory took issue with the aged Eutychius of Constantinople, who had recently published a treatise, now lost, on the General Resurrection. Eutychius maintained that the resurrected body "will be more subtle than air, and no longer palpable".