Guillaume de Bray (born at Bray in the Ile-de-France, date unknown; died in Orvieto, 29 April 1282) was a French ecclesiastic and Roman Catholic Cardinal, poet, and mathematician.
It is claimed Guillaume was Master of Theology, but the Cardinal's tombstone indicates that he was learned in Canon and Civil Law. There is no reference to him ever having been a Papal Legate, a Nuncio, or a provincial Rector (governor). So far as it is known, his career as a cardinal was entirely inside the Roman Curia.