William X of Aquitaine (1099 – April 9, 1137), nicknamed the Saint was Duke of Aquitaine and Gascony and Count of Poitiers as William VIII of Poitiers between 1126 and 1137. He was the son of William, the Troubador by his wife, Philippa of Toulouse .

William was born in Toulouse during the brief period when his parents ruled the capitol. Later that same year, much to his wife's ire, Duke William mortgaged Toulouse to Philippa's cousin, Bertrand of Toulouse, and then left on Crusade. Philippa and her infant son were left in Poitiers. When Duke William returned, he took up with Dangereuse, the wife of one of his vassals, and set aside his rightful wife, Philippa. This caused conflict between father and son, until William married married Ænor of Châtellerault, daughter of his father's mistress, in 1121. He had from her three children: William Aigret, who died young; the heiress Eleanor of Aquitaine; and Petronilla of Aquitaine, who married Raoul I of Vermandois . Both Ænor and William Aigret died in 1130.

As his father before him, William X was a patron of troubadors, music and literature. He was an educated man and strived to give his two daughters an excellent education, in a time when Europe's rulers where hardly literate. When Eleanor succeeded him as Duchess, she continued William's tradition and transformed the Aquitanian court in of Europe's centre of knowledge.

Despite his love of the arts, William was not a peaceful man, and was frequently involved in conflicts with the neighbouring Normandy (which he raided in 1136) and France. Even inside his borders, William faced an alliance of the Lusignans and the Parthenays against him, an issue resolved with total destruction of the enemies. In international politics, William X initially supported antipope Anacletus II in the schism of 1130, opposite to Pope Innocent II, against the will of his own bishops. In 1134 Saint Bernard of Clairvaux convinced William to drop his support to Anacletus and join Innocent.

In 1137 William joined the pilgrimage to Santiago de Compostela, but died of food poisoning during the trip. On his deathbed, he expressed his wish to see king Louis VII of France as protector of his fifteen year old daughter Eleanor. Louis VII accepted this wish and married the heiress of Aquitaine.

See also: Dukes of Aquitaine family tree

Sources

• Parsons, John Carmi. Eleanor of Aquitaine: Lord and Lady, 2002