William V (969 – 31 January 1030), called the Great (le Grand), was Duke of Aquitaine and Count of Poitou (as William II or III) from 990 until his death. He was the son and successor of William IV by his wife Emma of Blois, daughter of Theobald I of Blois. He seems to have taken after his formidable mother, who ruled Aquitaine as regent until 1004. He was a friend to Bishop Fulbert of Chartres, who found in him another Maecenas, and founded a cathedral school at Poitiers. He himself was very well educated, a collector of books, and turned the prosperous court of Aquitaine into the learning centre of Southern France.