William IV, Count of Toulouse

William IV of Toulouse (c. 1040 – 1094) was Count of Toulouse, Margrave of Provence, and Duke of Narbonne from 1061 to 1094. He succeeded his father Pons of Toulouse upon his death in 1061. His mother was Almodis de la Marche, but she was kidnapped by and subsequently married to Ramon Berenguer I, Count of Barcelona when William was a boy. He was married to Emma of Mortain (daughter of Robert, Count of Mortain and a niece of William of Normandy), who gave him one daughter, Philippa. He also had an illegitimate son, William-Jordan, with his half-sister Adelaide.

He married twice, and produced two legitimate sons; neither, however, survived infancy, leaving daughter Philippa as his heiress. As Toulouse had no tradition of female inheritance, this raised a question with regard to succession. In 1088, when William departed for the Holy Land, he left his brother, Raymond of Saint-Gilles, to govern in his stead (and, it was later claimed, to succeed him). Within five years, William was dead, and Raymond in a perfect position to take power – although, after Philippa married William IX of Aquitaine, they laid claim to Toulouse and fought, off and on, for years to try to reclaim it from Raymond and his children.

He was the great-grandfather of Eleanor of Aquitaine, by his daughter's marriage to William IX of Aquitaine, and Eleanor's descendants would continue to lay nominal claim to Toulouse based on descent from William IV.