Léon Gustave Schlumberger (17 October 1844 – 9 May 1929) was a French historian and numismatist who specialised in the era of the crusades and the Byzantine Empire. His Numismatique de l'Orient Latin (1878–82) is still considered the principal work on the coinage of the crusades.[1] He was awarded the medal of the Royal Numismatic Society in 1903. A large portion of his extensive Crusader coin collection is housed in the Cabinet des Médailles a department of the Bibliothèque nationale de France in Paris.