Pope Joan was, according to legend, a woman who reigned as pope for two years during the Middle Ages. Her story first appeared in chronicles in the 13th century and subsequently spread throughout Europe. The story was widely believed for centuries, but most modern scholars regard it as fictional.

Pope Leo IV was the bishop of Rome and ruler of the Papal States from 10 April 847 to his death. He is remembered for repairing Roman churches that had been damaged during the Arab raid against Rome, and for building the Leonine Wall around Vatican Hill to protect the city. Pope Leo organized a league of Italian cities who fought and won the sea Battle of Ostia against the Saracens.