William of Saint-Omer () can refer to several members of the House of Saint Omer:
William I of Saint-Omer, castellan of Saint Omer William II of Saint-Omer, castellan of Saint Omer William III of Saint-Omer, castellan of Saint Omer William IV of Saint-Omer (died 1191), castellan of Saint Omer William V of Saint-Omer (ca. 1170–1246), castellan of Saint Omer William VI of Saint-Omer, castellan of Saint Omer William VII of Saint-Omer, castellan of Saint Omer William of Saint-Omer (son of Nicholas I), Master of the Horse of Hungary William of Saint-Omer (son of Walter of Tiberias), Crusader noble