John Damian de Falcuis (Italian: Giovanni Damiano de Falcucci) was an Italian at the court of James IV of Scotland. His attempts at medicine, alchemy, flying, and his advancement by the king encouraged a satirical attack by the poet William Dunbar.
In the records of the Scottish exchequer he is called the 'French Leech' or 'Master John the French Leech' ('leech' being an old word for a physician). He first appears in the records in January 1501. He directed the building of alchemical furnaces at Stirling Castle and Holyroodhouse to produce the quinta essentia, the fifth element. John was then made Abbot of Tongland. Between 1501 and 1508 he received a great deal of money and other items from the king, to make the quintessence. These included aqua vitae (i.e. spirits of wine), quicksilver, sal ammoniac, alum, litharge, orpiment, saltpetre, silver, sugar, sulphur, tin, verdigris, vinegar and white lead. These are all standard alchemical substances of the medieval period.
John took a hand in court entertainments, organizing the dances in Edinburgh at New Year 1504. In 1507, John tried to fly from the battlements of Stirling Castle, but broke his thigh in the process. The records of Scottish exchequer list sums of money lost by the King playing cards with John and betting at shooting matches. John resigned as Abbot of Tongland in 1509, and James IV wrote to Pope Julius II asking that John's pension of 200 gold ducats should be paid. John Damian is still recorded at court a few months before the battle of Flodden.