In the time of Pepin the Short, the wife of Thierry, count of Toulouse, gave birth to a son to whom they gave the name of William. Upon attaining man hood William went to court, where he soon became a favourite with Charlemagne, who by this time had succeeded to his father's throne. He filled various offices to the monarch's satisfaction and then was sent by him against the Saracens who were threatening France. At the same time he was created duke of Aquitaine. William vanquished the Saracens, and raised the prestige of Christianity amongst the Moslems by his bravery, justice and piety. Amongst those of his own faith also he came to be regarded as the ideal Christian knight, and he figures as the principal character in several chansons de geste, such as La prise d'Orange and Aliscans. He could not, however, rest satisfied with serving his king; he desired to place himself at the disposal of the King of kings. With this object in view he sought for a suitable site on which to build a monastery, and discovered it at Gellone, at about an hour's distance from the celebrated abbey of Aniane. There he founded his monastery, which he peopled with monks from the neighbouring religious houses, especially from Aniane. He also built in the vicinity a convent for women, in which his sisters took the veil.

For some time William continued to live in the world, attending the royal court, where he was regarded with great favour, but the call to abandon all came to him as it had done to his sisters. He obtained the requisite permission from Charlemagne, and then made his way to Brioude in the Auvergne, where he hung up his weapons in the church of St Julian after he had laid an offering on the altar. From thence he went to Gellone, where he received the habit from St Benedict of Aniane, who became from that time his director and spiritual guide. Perfect as had been St William's conduct as a layman, it was equally perfect as a monk. He died on May 28, 812, and was buried in his own monastery, which was afterward renamed William in the Wilderness.

The life printed in the Acta Sanctorum, May, vol. vi, cannot be the work of a contemporary, as it purports to be, but it is relatively sober. See " L. Clarus" (W. Volk), Herzog Wilhelm von Aquitanien (1865); G. Morin in the Revue Charlemagne, vol. ii (1913), PP. 116-126 -, A. Becker, Die alt-französische Wilhelm-sage (1896); Bédier, Les Légendes épiques (1926), t. i.