William of Modena, Italian bishop and diplomat

William of Modena, also known as William of Sabina, Guglielmo de Chartreaux, Guglielmo de Savoy, Guillelmus, was an Italian clergyman and papal diplomat. He was frequently appointed a legate, or papal ambassador by the popes Honorius III and Gregory IX, especially in Livonia in the 1220s and in the Prussian questions of the 1240s. Eventually he resigned his see to devote himself to these diplomatic issues. On 28 May 1244 he was created Cardinal-Bishop of Sabina by Pope Innocent IV. For a short time (1219–1222) he served also as Vice-Chancellor of the Holy Roman Church.