Guillaume de Nangis (died 1300), also known as William of Nangis, was a French chronicler. William was a monk in the Abbey of St.-Denis to the north of Paris. About 1285 he was placed in charge of the abbey library as custos cartarum, and he died in June or July 1300. Having doubtless done some work on the Latin manuscripts on which the Grandes Chroniques de France are based, William wrote a long Chronicon, dealing with the history of the world from the creation until 1300. For the period before 1113 this work merely repeats that of Sigebert of Gembloux and others; but after this date it contains some new and valuable material. The chronicle had later continuations by other authors, with the "second continuation", mainly by Jean de Venette, taking events up to 1368.