Popes with the longest reigns The NUMBER@1 longest-reigning popes whose reign lengths can be determined from contemporary historical data are the following : Pius IX -LRB- NUMBER@2 NUMBER@3 -RRB- : NUMBER@4 years , NUMBER@5 months and NUMBER@6 days -LRB- NUMBER@7 days -RRB- .

Popes with the longest reigns The NUMBER@1 longest-reigning popes : PERSON@1 -LRB- NUMBER@2 NUMBER@3 -RRB- : NUMBER@4 years , NUMBER@5 months and NUMBER@6 days -LRB- NUMBER@7 days -RRB- .
