The Pope Joan Myth
From the 13th to the 17th centuries, there was a persistent legend, told both within the Roman Catholic Church and by the Church's enemies, that a woman had once served as pope. In the most common version of the tale, a young woman from Mainz who had studied in Athens, dressed as a man, settled in Rome as a cleric and was elected pope as "John Anglicus," styled as John VIII, after the death of Leo IV in 855. Her real gender was exposed two years later, however, as she rode in a procession from St. Peter's to the Lateran, giving birth to a child (from a secret liaison with a secretary-deacon) on a narrow street between the Colosseum and S. Clemente. Enraged, Roman onlookers are said to have tied her to her horse's tale, dragged her around the city in disgrace and stoned her to death, to be succeeded by Benedict III.
Her first "biographer" was a 13th century senior scholar within the Church and later the archbishop of Gneisen, Martin Polonus, who acknowledged her existence in his otherwise dispassionate chronicle of popes, but observed that because of her fraud she was not included in the official papal registry. Subsequent writers, including Petrarch and Boccaccio, embellished the tale, but the basic facts seem to have been accepted as truth by the Church and its partisans for a few centuries -- a bust of Pope Joan had stood among the gallery of pontiffs in Siena Cathedral until 1601, and allegedly John XXI had accounted for Joan in numbering himself as the XXIst John in the papal list.
Catholic writers began to bristle at the notion of a female pope in the 16th century, but the legend was considered "demolished" by a Protestant writer, David Blondel in the 1650s. Nonetheless, modern proponents of the "Pope Joan" myth point to some unusual traditions which seem to have grown up within the Church as evidence of her existence -- including the curious pontifical election ritual practiced from the 10th to the 16th centuries in which the selected candidate was required sit in a birth-chair with a hole underneath at the time of investiture, allegedly so that a representative cardinal could inspect the candidate's gender, and the tradition that subsequent popes allegedly avoided the narrow street on which Joan supposedly gave birth. Subsequent soundings of the "Pope Joan" story include Emmanuel Royidis' novel Pope Joan (1954), a film starring Liv Ullmann (1972) and a popular Victorian card game.