Pope St. Leo I, called Leo the Great, led the Church from 440 to 461, defended the true faith about Christ at the Council of Chalcedon, and twice protected Rome from barbarian invaders. He is a Doctor of the Church, and his sermons are still read in the Liturgy of the Hours, above all his Christmas sermon: “Christian, acknowledge thy dignity.” His feast is November 10, which in 2026 falls on a Tuesday. Below are his life, his best-known words, the prayer of his feast, and the popes who have taken his name, down to Pope Leo XIV.
Who was St. Leo the Great?
- A Roman deacon. According to the Liber Pontificalis, Leo came from Tuscany. By the 430s he was an influential deacon of the Church of Rome under Pope Celestine I and Pope Sixtus III, and the imperial court sent him to Gaul to make peace between two quarreling officials.
- Pope. While he was away in Gaul, Sixtus III died, and Leo was elected his successor. He was consecrated on September 29, 440, and governed the Church for twenty-one years.
- Shepherd of Rome. He preached regularly to the people of Rome, fought the Manichaean sect that had taken refuge in the city, and insisted on the unity of the Church under the successor of Peter.
- The Tome of Leo. When a monk named Eutyches taught that Christ had only one nature after the Incarnation, Leo wrote his famous letter to Bishop Flavian of Constantinople (449), the Tome, explaining that Christ is one Person in two natures, truly God and truly man.
- Chalcedon. The Council of Chalcedon (451) accepted the Tome as an expression of the Catholic faith. Tradition remembers the bishops acclaiming it with the words “Peter has spoken through Leo.”
- Attila and Genseric. In 452, when Attila and the Huns had ravaged northern Italy, Leo went to meet him near Mantua and persuaded him to withdraw. In 455, when the Vandals under Genseric captured Rome, Leo’s intercession obtained the promise that the inhabitants would be spared.
- Death. He died on November 10, 461, and is buried in St. Peter’s Basilica beneath an altar dedicated to him. Pope Benedict XIV declared him a Doctor of the Church in 1754.
“Christian, acknowledge thy dignity”
Leo’s ninety-odd surviving sermons are short, clear and rhythmic, written to be heard. His first sermon on the Nativity contains his most quoted lines, read every Christmas in the Office of Readings:
Christian, acknowledge thy dignity, and becoming a partner in the Divine nature, refuse to return to the old baseness by degenerate conduct. Remember the Head and the Body of which thou art a member. Recollect that thou wert rescued from the power of darkness and brought out into God’s light and kingdom. By the mystery of Baptism thou wert made the temple of the Holy Ghost.
Leo also explained why the Church fasts at the turn of each season; see the Ember Days.
The prayer of his feast
The Collect for St. Leo in the traditional Roman Missal, where his feast was kept on April 11:
Hear, we beseech thee, O Lord, our prayer which we make on the feast of thy blessed Confessor and Bishop Leo, and by the prayerful merits of one who deserved to be thy worthy servant, absolve us from all our sins. Through Jesus Christ, thy Son our Lord, who liveth and reigneth with thee in the unity of the Holy Ghost, God world without end. Amen.
A prayer to St. Leo the Great
Written for this page:
St. Leo the Great, you defended the truth that Jesus Christ is true God and true man,
and you went out unarmed to protect your people from the invader.
Pray for the Pope and for all the shepherds of the Church,
that they may teach the faith clearly and guard their flocks with courage.
Help me to remember my dignity as a child of God, and to live worthy of it.
St. Leo, pray for us. Amen.
The popes named Leo
Fourteen popes have taken the name Leo, many of them in honor of Leo the Great. Among the best known:
- St. Leo III (795–816), who crowned Charlemagne emperor on Christmas Day, 800.
- St. Leo IX (1049–1054), a reforming pope who fought simony.
- Leo X (1513–1521), the Medici pope of the Renaissance and of the beginning of the Protestant Reformation.
- Leo XIII (1878–1903), author of Rerum Novarum (1891), the founding document of modern Catholic social teaching, and of the Prayer to St. Michael.
- Leo XIV, elected on May 8, 2025, the first pope from the United States, who explained that he chose his name in part because of Leo XIII and the Church’s social teaching in a new industrial revolution. See the prayer for the Pope.
Frequently asked questions
When is the feast of St. Leo the Great?
November 10, the day he died in 461. It is an obligatory memorial. Before 1969 his feast was kept on April 11.
Why is he called “the Great”?
Because of his teaching on Christ, which shaped the Council of Chalcedon, his defense of Rome against Attila and Genseric, and his firm leadership of the Church in a time of collapse. Only two other popes are commonly called “the Great”: Gregory I and Nicholas I.
Did Pope Leo really stop Attila the Hun?
In 452 Leo met Attila near Mantua, and Attila withdrew from Italy soon after. Historians debate the reasons, which may have included famine and disease in his army, but contemporaries credited Leo’s embassy.
More saints and prayers
- St. Gregory the Great
- Chair of St. Peter
- Prayer for the Pope
- St. Peter
- Nicene Creed
- Athanasian Creed
- Ember Days
- Saint of the day
Texts and sources
- Leo the Great, Sermon XXI (On the Feast of the Nativity I), chapter 3, translated by C. L. Feltoe, Nicene and Post-Nicene Fathers, second series, vol. 12 (1895), public domain (Wikisource).
- Collect: The Mass Every Day of the Year (1916 daily missal), April 11, public domain (archive.org). OCR errors corrected.
- Johann Peter Kirsch, “Pope St. Leo I (the Great),” Catholic Encyclopedia, vol. 9 (1910), Wikisource.