The longest-serving pope in history is traditionally recognized as Saint Peter, the first pope, who is said to have reigned for approximately 34 to 37 years (around 30–64 or 67 AD)

. However, many historians dispute the exact length of his papacy because the precise starting date is not verifiable. Among popes with well-documented reigns, Pope Pius IX holds the record for the longest verified papacy, serving for 31 years, 7 months, and 23 days from 1846 to 1878

. In summary:

• Saint Peter: about 34 to 37 years (traditional, but disputed)
• Pope Pius IX: 31 years, 7 months, and 23 days (longest verified reign)