William I (22 March 875 – 6 July 918), called the Pious, was the Count of Auvergne from 886 and Duke of Aquitaine from 893, succeeding the Poitevin ruler Ebalus Manser.

Sometime before 898, William married the Bosonid Angilberga, daughter of Boso of Provence and Ermengard of Italy.

In 909, William founded the Benedictine abbey of Cluny that would become an important political and religious centre.

[2] William required no control over the abbey, which he arranged should be responsible directly to the pope (see Clunian reforms).

A sign of William's independence of rule in Aquitaine is that he had a deniers minted in his own name at Brioude.