Original: Popes with the longest reigns The 10 longest-reigning popes whose reign lengths can be determined from contemporary historical data are the following : Pius IX ( 1846 1878 ) : 31 years , 7 months and 23 days ( 11,560 days ) .
Simplified: Popes with the longest reigns The 10 longest-reigning popes : Pius IX ( 1846 1878 ) : 31 years , 7 months and 23 days ( 11,560 days ) .