Nicholas, or Nicolas Flamel, was a French alchemist who lived in the fifteenth century. His life is no myth: his house in Paris, built in 1407, still stands, at 51 rue de Montmorency, where it has been made into a restaurant. His deeds, though, are the stuff of legend.
Flamel is supposed to have been the most accomplished of the European alchemists. It is claimed that he succeeded at the two magical goals of alchemy supposed to have been the chief aims of that pseudoscience: he made the Philosopher's Stone that turns lead into gold, and he and his wife Perenelle achieved immortality.
Flamel is supposed to have received a mysterious book from a stranger, full of qabalistic words, in Greek and Hebrew. Flamel made the understanding of this text of lost secrets his life's work, travelling to universities in Andalusia to consult with Jewish and Muslim authorities. In Spain, he met a mysterious master who taught him the art of understanding his manuscript.
After his return from Spain, Flamel was able to become rich: the knowledge that he gained during his travels made him a master of the alchemical art. Flamel became a philanthropist, endowing hospitals and churches with the proceeds from his alchemical work. He caused arcane alchemical signs to be written on a tombstone, which is preserved at the Musée de Cluny in Paris. His tomb is empty; some say it was sacked by people in search of his alchemical secrets. On the other hand, if he in fact achieved the secret of immortality, his empty tomb may have another explanation.
Nicholas Flamel's story is alluded to in the first Harry Potter book, Harry Potter and the Philosopher's Stone (or, Sorcerer's Stone).