What’s in a Name? History's Greatest Popes Named Leo

Matthew Neugebauer

Friday, May 16, 2025

Painting of an elderly St. Leo the Great, with a worn face and a long white beard.

St. Leo the Great. Herrera Mozo. Wikimedia Commons

Pope Leo XIV. The hopeful reality of a new Supreme Pontiff is starting to set in. The more I see of him, hear him speak (including in his native English!), and see his name, the more familiar this new era in the Church's life feels.

So, what's in a name? When a new pope chooses a name that's been used before, it’s usually to highlight some of his predecessors or other historical figures, as ways of recalling the importance of their legacy in the present day.

For example, in 2005 Benedict XVI chose his name to honour both St. Benedict of Nursia, the father of western monasticism, and Pope Benedict XV, who bucked popularity by calling for peace during World War I. In a new century marked by a more dominant secularism in the West and an increasing clash of globalized civilizations, Benedict XVI focused on forming a smaller, more faithful European Church that freely proclaimed the peace of Christ.

When Pope Francis chose his name, it signalled that his pontificate would be marked by calling for a renewed relationship with our common home and all the creatures who live here, and a renewed fraternity between nations, peoples, and persons. He named his pair of landmark social encyclicals, Laudato Si’ and Fratelli Tutti, after poetic prayers by the great mystic of Assisi.

As for Pope Leo XIV – he explicitly mentioned the most recent predecessor to bear the name, Leo XIII (1878-1903). I’ll get to him shortly as well as in a separate blog post, after I mention some earlier examples that stand out as well:

St. Leo III (795-816) is perhaps best known for his diplomatic relationship with the Frankish ruler Charlemagne. That dialogue proved mutually beneficial, especially when Leo crowned Charlemagne as the first western Roman Emperor in three centuries, on Christmas Day, 800 CE. He was canonized by Pope Clement XI in 1673.

St. Leo IX (1049-1054) was a reforming pope who renewed the requirement for clerical celibacy and rooted out simony (selling ecclesiastical services) and other forms of corruption. However, his pontificate saw weakened relations with the Eastern Church, which led to the Great Western Schism in the last year of his reign. He was canonized by Pope Gregory VII 28 years later in 1082.

Undoubtedly, the most important pope in this "list of Leos" is St. Leo I (440-461), Latin Father and Doctor of the Church. He was the first pope to officially receive the title "the Great," followed by St. Gregory and St. Nicholas. St. Leo the Great’s most enduring contribution was to our doctrine of Jesus the Son of God: he wrote convincingly on Christ's union-in-distinction between Divine and human natures. This doctrine, later called the “hypostatic union,” was then affirmed at the Council of Chalcedon in 451, and continues to be the standard of Catholic faith to this day. Recognition of his sainthood predates the formal canonization process, but he was named the Doctor of the Unity of the Church by Pope Benedict XIV in 1754.

The extraordinarily long 25-year pontificate of Pope Leo XIII immediately followed the even longer 32-year pontificate of Blessed Pius IX. During his turn-of-the-century reign, he promulgated regulations for simpler and more traditional music in the liturgy, began a more constructive relationship with the new Italian Republic, and even composed the well-known St. Michael Prayer! He may be best known as the father of modern Catholic Social Teaching, which formally begins with his 1891 encyclical Rerum Novarum. Yesterday, May 15, was the 134th anniversary of its promulgation!

This brings us to Pope Leo XIV’s choice of name. In his Address to the College of Cardinals this past weekend, our new pope explained that he chose it primarily since

Pope Leo XIII in his historic encyclical Rerum Novarum addressed the social question in the context of the first great industrial revolution. In our own day, the Church offers to everyone the treasury of her social teaching in response to another industrial revolution and to developments in the field of artificial intelligence that pose new challenges for the defence of human dignity, justice, and labour.

I’ll spend more time reflecting on the potential importance of Rerum Novarum for these 21st-century challenges in a future article. Stay tuned to our blog, and visit slmedia.org/pope-leo-xiv for our latest coverage of this fourteenth Leonine papacy.