Longest Reigning Popes

See Also: Recent Popes | Conclave 2005

#	Pope	Election	Installation	Death	Length (E)	Length (I)
1	St. Peter	exact dates unknown			roughly 35 years
2	Bl. Pius IX	16 Jun 1846	21 Jun 1846	7 Feb 1878	31.6	31.6
3	John Paul II	16 Oct 1978	22 Oct 1978	2 Apr 2005	26.4	26.4
4	Leo XIII	20 Feb 1878	3 Mar 1878	20 Jul 1903	25.4	25.4
5	Pius VI	15 Feb 1775	22 Feb 1775	29 Aug 1799	24.5	24.5
6	Adrian I	1 Feb 772	9 Feb 772	25 Dec 795	23.9	23.9
7	Pius VII	14 Mar 1800	21 Mar 1800	20 Aug 1823	23.4	23.4
8	Alexander III	7 Sep 1159	20 Sep 1159	30 Aug 1181	22.0	21.9
9	St. Sylvester I	31 Jan 314		31 Dec 335	21.9
10	St. Leo I (the Great)	29 Sep 440		10 Nov 461	21.1
11	Urban VIII	6 Aug 1623	29 Sep 1623	29 Jul 1644	21.0	20.8
12	St. Leo III	26 Dec 795	27 Dec 795	12 Jun 816	20.5	20.5

Dates taken from the Annuario Pontificio 2005.

Average reign for a pope is roughly 7.5 years.
Benedict XVI is the 265th pope. (264rd successor to St. Peter)
Note that the decimal values in the table above are slightly off because they don't attempt to account for leap years and other calendar oddities