Answer
Pope Urban IV, who was elected in 1261, is one of only four popes who were not cardinals at the time of their election. The other three were Pope Marcellinus I (308–309), Pope Agapetus I (535–536), and Pope Gregory VI (1045–1046). Pope Marcellinus was elected after a disputed papal election, and his election was disputed by some who claimed that he was not a legitimate pope.