William of Montreuil (French: Guillaume de Montreuil) was an Italo-Norman freebooter of the mid-eleventh century. He was described by Amatus of Monte Cassino as an exceptional knight, small in stature, who was very robust, strong, valiant and by Orderic Vitalis as le Bon Normand, "the Good Norman."
He was a son of the Guillaume Giroie who journeyed to Apulia and died in Gaeta, and Emma. He too travelled to Italy, where he married a daughter of Richard I of Capua. This may have been the same daughter who was betrothed to the son of Atenulf I of Gaeta. Richard granted his adopted son the counties of Marsia, Campania, and Aquino as part of her dowry. In 1064, he was appointed Duke of Gaeta, but he repudiated his wife to marry Maria, widow of Atenulf I and daughter of Pandulf IV of Capua. He joined with Lando, Count of Traietto, a son of Atenulf, and besieged Aquino and Piedimonte, defended by Atenulf's other sons. He was unsurprisingly deprived of Gaeta and forced to flee.
He then took service with Pope Alexander II and saw military action in the Reconquista in Iberian Peninsula, where he won his famous sobriquet. In 1064, as the gonfalonier of the cavalry of Rome, he was present at the siege of Barbastro, where he took an enormous booty [1]. He was equally successful on behalf of the pope in the Campania.
He granted two churches to Monte Cassino in September 1068 and died in Rome of a fever.[2]
| Preceded by Atenulf II |
Duke of Gaeta 1064 |
Succeeded by Lando |