William of Montreuil (French: Guillaume de Montreuil) († aft. 1068), was an Italo-Normanfreebooter of the mid-eleventh century who was briefly Duke of Gaeta. 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 ‘the good Norman’ (Latin: le bon Normand).
He was a son of William fitz Giroie Lord of Échauffour and Montreuil-l’Argillé and Emma de Tannei, daughter of Walchelin de Tannei. By a charter to the Abbey of Saint-Evroul in 1050, William was still in Normandy at that time. Like his father and brother he granted all the monasteries he possessed, in return “for no small sum”, to the abbey of Saint-Evroul. With his brother Arnold consenting, he granted the abbey his mills, farms and fisheries. Before leaving Normandy he also donated a farm of one plough, situated at Verneuces, to the abbey of Saint-Evroul “for the redemption of the soul of his mother Emma.”
William left Normandy for Italy before 1056. At some point he joined forces with Richard I Drengot, who became Prince of Capua in 1058. Richard both adopted William as his son and gave him his daughter’s hand in marriage. Richard granted his son-in-law the unconquered counties of Marsia, Campania, and Aquino as part of her dowry, giving William the title of Duke of Gaeta. The prince then ceded control of Gaeta to William, but he soon revolted and attempted to repudiate his wife[lower-alpha 1] after which he planned to marry Duchess Maria, widow of Atenulf I, the former Duke of Gaeta. He joined together with Count Atenulf of Aquino,[lower-alpha 2]Lando, Count of Traietto, and Lando’s son Peter to free themselves of Prince Richard’s control and keep their castles. William obtained some help from friends in Apulia consisting of donations and knights to support him and returned to hold Traetto against the prince. The prince in turn encamped near Traetto across the Garigliano river and for months the two sides engaged in small skirmishes. Finally, short of supplies William and his companions left Traetto for Aquino, where they parted each going his own way. William returned to the castle of Piedimonte trying to gather supplies but with little success.
Prince Richard next acted to break up the coalition between William, Atenulf, Lando and the Duchess Maria. He arranged for Maria to wed his son, Jordan (who he had also made a prince), which offer the duchess readily accepted. Next the prince offered Lando the hand of another daughter, which Lando humbly accepted. He then made Lando Duke of Gaeta in William’s place. William was still married to the prince’s daughter and by the intercession of William’s friends, asked the prince’s forgiveness. The prince returned William’s wife and heaped riches on him (although there was no further mention of William becoming a duke). It was also at this time the peasants of the castle of Piedimonte rebelled and all the Normans William had left to guard the castle were killed, which disturbed William greatly.
William rebelled against Prince Richard a second time,[lower-alpha 3] apparently emboldened by the lands originally given him by the prince had since been regranted by the pope. William assumed he could count on the pope opposing his master Richard, so he began burning the prince’s towns. After suffering this injury to his realm Richard finally sent his son Jordan against William with two hundred and sixty knights. Not being able to locate William or his troops, Jordan and his knights raided William’s territories carrying off a great deal of plunder. By this time William had been away at Rome and on his return he asked that the animals be returned to him as they hadn’t been plunder, it was robbery[lower-alpha 4] since William had been away at the time. Jordan refused claiming William broke his oath of fealty. William furious with this reply took his eight hundred knights and three hundred infantry and attacked Jordan. According to Amatus, the plunder was abandoned and Jordan and his knights fled the battle after losses on both sides. William then returned to Aquino. Prince Richard then asked for help from Duke Robert in dealing with William, but before anything could be organized it was learned that William had died.