The length of a pope's reign varies widely throughout history. Here are some of the longest-reigning popes:

• Saint Peter, regarded as the first pope, is traditionally believed to have served for about 34 to 37 years (c. 30–64 or 33–67 AD), though exact dates are uncertain

• Pope Pius IX reigned for 31 years, 7 months, and 23 days (1846–1878), the longest verified papacy in modern history

• Pope John Paul II served for 26 years, 5 months, and 17 days (1978–2005)

• Pope Leo XIII reigned for 25 years, 5 months, and 1 day (1878–1903)

• Pope Francis, the most recent pope who died in April 2025, served nearly 12 years from March 2013 to April 2025

In general, the average length of a papacy since 1900 has been about 12 years

. The length depends on the pope's age at election and health during the pontificate. Thus, popes have reigned anywhere from a few years to over three decades, with Saint Peter traditionally considered the longest-serving pope, followed by Pius IX with the longest verified tenure. Pope Francis served nearly 12 years until his death in 2025