Guillaume de Montfort, (died 27 September 1432,[1] Siena, Italy) was a 15th-century French cleric, Bishop of Saint-Malo and cardinal.
Entering the church at a young age, Montfort was appointed protonotary apostolic and Archdeacon of Dinan.
On 29 May 1424, he demonstrated his opposition to John V, Duke of Brittany, who was constructing a dungeon at the château of Saint-Malo, by throwing a stone.
He died suddenly en route, possibly poisoned,[2] on 27 September 1432, and was buried in the church of the Cordeliers in Siena.
All his acts portray for us a pastor full of kindness for his flock, at home with his canons as with his equals, affable and benevolent to all, of an exemplary conduct, and in all, enjoying the reputation of a saint