Longest-reigning popes — With the resignation of Pope Benedict, take a look at history's longest-reigning popes, or check out history's shortest-reigning popes.No. 10 (10th longest-reigning pope): Pope Urban VIII reigned for 20 years, 11 months and 24 days from 1623 to 1644. Hulton Archive/Getty Images Longest-reigning popes — No. 9: Leo I, both a pope and saint, reigned from 440 to 461, for a total of 21 years, 1 month and 13 days. Spencer Arnold/Getty Images Longest-reigning popes — No. 8: Pope Sylvester I reigned from 314 to 335 for a total of 21 years, 11 months and 1 day. Spencer Arnold/Getty Images Longest-reigning popes — No. 7: Pope Alexander III reigned for 21 years, 11 months and 24 days. Spencer Arnold/Getty Images Longest-reigning popes — No. 6: Pope Pius VII reigned from 1800 to 1823 for a total of 23 years, 5 months and 7 days. Hulton Archive/Getty Images Longest-reigning popes — No. 5: Pope Adrian I reigned for 23 years, 10 months and 25 days, from 772 to 795. Spencer Arnold/Getty Images Longest-reigning popes — No. 4: Pope Pius VI reigned from 1717 until his imprisonment, and subsequent death, in 1799. His reign lasted 24 years, 6 months and 15 days. Hulton Archive/Getty Images Longest-reigning popes — No. 3: Pope Leo XIII reigned from 1878 to 1903, totaling 25 years, 5 months and 1 day. Hulton Archive/Getty Images Longest-reigning popes — No. 2: Pope John Paul II reigned for 26 years, 5 months and 18 days, from 1978 to 2005. Gianni Ferrari/ Cover/Getty Images Longest-reigning popes — No. 1: Pope Pius IX reigned the longest of all popes, from 1846 to 1878, for a total of 31 years, 7 months and 23 days. Moling/Hulton Archive/Getty Images Prev Next