Pope Joan was the only female Pope in history. It isn't an error, fallacy or blasphemy. Research shows that she really existed. The months ahead spend as pope is obscure but facts show and points that she possibly existed.
The existence of a female Pope was so odd and absurd and thus the Catholic Church tried to bury the facts so as to extinguish the shame she stain it might bring to the church's body.
We're sorry if this article hurts your religious personality and historical beliefs but it's our duty to dig out facts from every aspect of life and so this is the religious fact we've dug out. Let's get back to the topic's points. 
"whenever you see a legend, you can be sure, if you go to the very bottom of things, that you will find history"- vallet de viriville.
Pope Joan is one of the most exceptional, extraordinary and amazing characters in western history and one of the least well known. Many people have never heard about this woman pope, Pope Joan and those who heard of her thought she was a legend or myth.
Yet for about six hundred years up to the seventeenth century, Joan's papacy was known and accepted universally to be true.
In the seventeenth century, the Catholic church under increasing attacks of Protestantism began a very scrubs crusade to blot out the knowledge of the existence of a female Pope in modern history. Hundreds of books and records written about Joan's existence as a pope were seized and destroyed, their writers were punished and threatened.
Joan lived in the ninth century during the dark ages. It was a time of widespread illiteracy marked by an extraordinary death of record keeping.
The was an Ancient copy of a book of records called liber pontificalis which contains records of popes that existed from centuries to centuries. This record showed that a pope named Joan under the guise of John existed.
Another striking evidence that points to Joan's existence was in 1276 when after a thorough search of the papal records, Pope John XX changed his title to John xxi in official recognition of Joan's reign as pope John viii, Joan's story was in the official church guidebook to Rome used by pilgrims for about Three hundred and Sixty Eight years.
Another piece of striking evidence that shows Joan existed as a pope was in the documented trial Of Jan Hus for Blasphemy. Jan Hus was charged for preaching the Heretical doctrine of the fallibility of a pope. All the Cardinals, patriarchs, metropolitans, Bishops and theologians that served as Jury during his trial Tagged all but one of his defense as blasphemy. The Statement he made that escaped the term BLASPHEMY was this
"Many times have the popes fallen into sin and error, for instance when Joan was elected pope, who was a woman". Not one of the twenty eight cardinals, four patriarchs, thirty metropolitans, four hundred and four theologians, and two hundred and six bishops present charged Hus with Blasphemy or fallacy.
The liber pontificalis was written majorly by a man named Anastasius, this papal librarian for Pope Nicholas.
This history as being dead long ago. But now it's being reawakened.. Make your research about Pope Joan, if it's a fallacy, the comment box is available for Use.