Taken as a whole, medieval monks and clerics were probably the most prolific forgers of all time.

• The Donation of Constantine (circa 750 ad)
  A forgery legitimated the Catholic Church's acquisition of vast territories in western Europe.
• Count d’Armagnac’s Forged Papal Bull (circa 1455)
  This French Count convinced a church official to forge a papal bull allowing him to marry his sister.
• The History of Crowland (1413)
  The monks of Crowland wrote a history of their abbey that was essentially a long string of lies.
• Jean Hardouin’s Theory of Universal Forgery (circa 1693)
  Hardouin was convinced that almost all classical texts had been forged by a group of thirteenth-century monks.

Throughout the Middle Ages, Europe hosted a thriving trade in holy relics. Many of the relics, if not almost all of them, were fake.

• The Holy Foreskin (First appeared circa 800 ad)
  Of all the relics that circulated throughout medieval Europe, the Holy Foreskin was the most sought after, since it was an actual body part of Christ. But there were many Holy Foreskins to choose between.
• The Shroud of Turin (circa 1355)
  If the Shroud of Turin isn't a divine miracle, then it's very likely to be the work of a medieval forger.

Medieval knowledge of world geography was a strange mixture of fact and fantasy.

• The Letter of Prester John (circa 1165)
  In the mid-twelfth century, at a time when European rulers felt threatened by the growing power of Muslim nations on their borders, a letter suddenly appeared from Prester John, who described himself as a Christian king of great wealth and power living in the far east.
• The Travels of Marco Polo (circa 1298)
  Marco Polo is famous for his travels to China, but some modern scholars have questioned whether he ever actually went there.
• The Travels of Sir John Mandeville (circa 1371)
  The Travels of Sir John Mandeville was a fourteenth-century book that documented the travels of an English knight through Egypt, Ethiopia, India, Persia, and Turkey. The tales of this knight, though supposedly true, were bizarre by any measure.
• The Lost Island of Hi-Brazil (Late medieval period)
  A number of maps from the late-medieval period show an island called Hi-Brazil in the Atlantic. However, no one has ever been able to find this island.

In medieval culture, prophecy was considered to be a legitimate science. But some prophecies were more far-fetched than others.

• Medieval End of the World Hoaxes
• The Toledo Letter (1184)
• The Prophecies of Nostradamus (1555)
• Mother Shipton (Supposedly lived 1488-1561)

Men of the renaissance prided themselves on their collections of books and classical artifacts. This helped to create a lucrative market for fake books and fake artifacts.

• Michelangelo’s Cupid (1496)
• Cicero’s Consolatio (1583)
• The Voynich Manuscript (circa 1500)

• The Boy with the Golden Tooth (1593)
  Medical doctors argued over how a Silesian boy managed to grow a golden tooth.
• A Case of Pregnancy without Intercourse (1637)
  A pamphlet published in Paris described an unusual medical case in which a woman claimed she became pregnant after dreaming of her husband, who had been away for four years.
• Lusus Naturae
  Medieval naturalists believed that Nature was an active, sentient force that enjoyed playing jokes (or hoaxes) on man.

• Athanasius Kircher, Victim of Pranks (1602-1680)
• The Cerne Abbas Giant (circa mid-1640s)