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September 12, 2026Short & citedBlog
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Civic Brief • Religion

Pope Leo

Pope Leo is the regnal name used by fourteen popes of the Catholic Church, from Leo I in the 5th century to Leo XIV, elected in 2025.

Updated September 12, 20261 min readCited sources

Pope Leo is the regnal name used by fourteen popes of the Catholic Church, from Leo I in the 5th century to Leo XIV, elected in 2025. The name is especially associated with Leo I “the Great,” Leo X of the Renaissance, and Leo XIII, known for his social teaching.

What it is

The name Leo has been used by fourteen popes across the history of the Catholic Church, beginning with Leo I in 440 and continuing most recently with Leo XIV. The list includes several saints and major historical figures.

Why it matters

Two popes named Leo stand out for their lasting impact. Leo I (440–461) strengthened papal authority and shaped Christological doctrine. Leo XIII (1878–1903) issued *Rerum Novarum*, a foundational document on Catholic social teaching that influenced labour rights worldwide.

Key details

Leo X (1513–1521), a Medici pope, is remembered for his role during the early Protestant Reformation and his conflict with Martin Luther. Leo XIV was elected in 2025, becoming the most recent pope to take the name.

In short

  • Fourteen popes have used the name Leo.
  • Leo I reigned from 440 to 461 and was later called 'the Great.'
  • Leo XIII is known for the encyclical *Rerum Novarum*.
  • Leo XIV became pope in 2025.
Canadian angle

Canadian Catholics and historians may encounter the name Leo most often in discussions of papal history, Catholic social teaching, and the Reformation; Leo XIII’s *Rerum Novarum* especially influenced Catholic social thought in Canada.

Quick questions

Who was Pope Leo?
“Pope Leo” refers to any of fourteen popes who took the name Leo, not one individual. The first was Leo I in 440, and the most recent was Leo XIV, elected in 2025.
Pope Leo X
Leo X was pope from 1513 to 1521. He was a Medici and is often remembered for his role during the early Protestant Reformation.
Pope Leo XIII
Leo XIII was pope from 1878 to 1903. He is best known for *Rerum Novarum*, an encyclical that became foundational in modern Catholic social teaching.

Sources

  1. Wikipedia — https://en.wikipedia.org/wiki/Pope_Leo
    Supports: List of popes named Leo and numbering through Leo XIV.
  2. Wikipedia — https://en.wikipedia.org/wiki/Pope_Leo_I
    Supports: Leo I dates, title 'the Great,' and papacy dates.
  3. Encyclopaedia Britannica — https://www.britannica.com/biography/Saint-Leo-I
    Supports: Leo I as pope from 440 to 461 and historical significance.
  4. Vatican News — https://www.vaticannews.va/en/saints/11/10/st--leo-the-great--pope-and-doctor-of-the-church.html
    Supports: Leo I as first pope named Leo, doctor of the Church, and burial in St. Peter's Basilica.
  5. Wikipedia — https://en.wikipedia.org/wiki/Pope_Leo_X
    Supports: Leo X dates, Medici identity, and death date.
  6. Wikipedia — https://en.wikipedia.org/wiki/Pope_Leo_XIII
    Supports: Leo XIII dates and papacy.
  7. Britannica Kids — https://kids.britannica.com/students/article/Leo-popes/275433
    Supports: Leo X as pope during the Reformation and connection to Luther.
  8. National Geographic — https://www.nationalgeographic.com/history/article/pope-name-pontiff-leo-meaning
    Supports: Leo I, Leo X and Leo XIII historical significance; Luther excommunication context.