William III (died after 1037) was the count and margrave of Provence from 1014 to his death.
He inherited the titles of his father Rotbold II but preceded his cousin William IV as count.
[1] His mother was Ermengarde, later the second wife of Rudolph III of Burgundy.
William had no known descendants and he left his margravial rights to his sister, Emma, who married William III Taillefer, Count of Toulouse, and thus brought the margravial title in Provence to the House of Toulouse.
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