Who is Nicolas Flamel?

Nicolas Flamel

A famous alchemist, the only known maker of the Sorcerer's Stone, and Professor Dumbledore's particular friend. Fearing that the Stone might be at risk, Flamel asked Professor Dumbledore to take the Stone to Hogwarts in order to give it the school's full protection. During the book, Flamel is already 665 years old (explaining why Harry, Ron, and Hermione had a difficult time learning his identity from the modern history textbooks in the library).

"Nicolas Flamel is the only known wizard who created the Sorcerer's Stone." <-- Hermione Granger