Why Do Popes Change Their Names After Being Elected?

A few days ago, when the new pope was elected, that familiar scene appeared on screens again: a man in a white cassock standing on the balcony, introduced to the world by a new name. And like many people, I had the same question in mind: why? Why does someone who was Robert until that moment speak to the crowd as Leo?

I looked into it a little, and what I found was much more human and much more pragmatic than I expected.

It All Started With A Pope Named “Mercury”

In 533, the man elected as the 56th pope of Rome was named Mercurius. In plain terms, his name was tied to Mercury, the Roman pagan god. He had reached the highest office in the Church, but his name still carried the echo of pagan mythology. He did not consider that appropriate, so he changed his name and became John II.

John II.

But this is the important part: that single act did not immediately become a permanent tradition. For centuries after Mercurius, many popes continued to serve under their birth names. The story paused there, until the practice slowly became almost a standard part of the papal office.

Peter Pig-Snout And A Turning Point

When the 142nd pope was elected, his birth name was Pietro Buccaporci. In English, this is usually rendered roughly as Peter Pig-Snout. As you can imagine, carrying that name while trying to preserve papal authority would not have been easy. He seems to have understood that as well, and took the name Sergius IV.

Sergius IV

When religious authority and the accident of birth did not fit together, changing the name became both an act of humility and a practical solution. There was also another sensitive point: the name Peter was avoided by popes out of respect for Saint Peter, who is traditionally considered the first pope.

After events like this, the custom gained strength. From around the 10th and 11th centuries onward, most newly elected popes chose a new name before beginning their papacy. That is still the case today.

Is It A Rule, Or Just A Custom?

Surprisingly, current Church law, the Codex Iuris Canonici, does not require a pope to change his name. There is no canon law that forces him to do it. But when something is repeated for centuries, it stops feeling like a simple tradition and becomes a norm. If a pope refused to do it now, people would immediately notice.

Technically, a pope can keep his baptismal name. But in the modern period, only a few exceptions did so. Adrian VI kept his birth name when he was elected in 1522. Later, in 1555, Marcellus II also kept his own name. Since Marcellus II, every pope has chosen a new papal name.

A Papal Name Is Not Random, It Is A Message

Popes usually choose names in honor of earlier popes or saints who inspire them. And that choice often hints at the kind of papacy they want to build.

Leo I, who served from 440 to 461, is remembered for standing against Attila the Hun at the gates of Rome. He became known as Leo the Great.

Leo XIII, who served from 1878 to 1903, became one of the major popes associated with social justice in the modern age. His encyclical Rerum Novarum, focused on workers’ rights and social balance, became a turning point in Catholic social teaching.

Pope Leo XIII became the first pope to appear on video with the film Sua Santità papa Leone XIII.

The new pope, Robert Francis Prevost, chose the name Leo XIV. Under the shadow of those earlier Leos, this is a meaningful choice: a mediator who stands firm in the face of power, and a reform-minded figure who places social justice at the center. The name is not an accident.

Robert Francis Prevost

A Small Historical Note: The Longest And The Most Unusual

One of the longest-serving popes in history was Pius IX. He remained in office for 31 years and 7 months. The collapse of the Papal States, the political unification of Italy, and the First Vatican Council all took place during his papacy.

For a long time, completely new and previously unused papal names were rare. Lando, in 913, was one of the last early examples of a pope associated with a name that did not become part of the usual repeated list. In 1978, John Paul I made a new two-name choice. In 2013, Francis chose a name never used before by a pope, inspired by Saint Francis of Assisi.

Popes have been connected to many strange historical stories beyond name changes. One of the darkest claims from World War II concerns Hitler’s alleged plan to kidnap Pope Pius XII and hold him prisoner in a castle. I covered that disturbing episode here: Hitler's Plan to Kidnap Pope Pius XII and Hold Him Prisoner in a Castle >>

Pope Pius XII

Conclusion: A Name Is A Manifesto

A pope is not legally required to change his name. But he does. And when he does, he is often telling us something: what kind of leader he wants to be, which legacy he wants to carry, and what he intends to stand against.

From Mercurius becoming John, to Pietro Buccaporci becoming Sergius, to Robert Prevost becoming Leo, this long line shows one thing clearly: names are sometimes more than labels. They can be statements of intent.

May Pope Leo XIV carry the weight of the name he has chosen.