Rabbi Sa'adiah ben Yosef Gaon (Arabic: سعيد بن يوصف الفيومي / סעיד בן יוסף אלפיומי Saʻīd bin Yūsuf al-Fayyūmi, Sa'id ibn Yusuf al-Dilasi, Saadia ben Yosef aluf, Sa'id ben Yusuf ra's al-Kull; Hebrew: רבי סעדיה בן יוסף אלפיומי גאון' or in short: סעדיה גאון; alternative English Names: Saadia b. Joseph, Saadia ben Joseph or Saadia ben Joseph of Faym or Saadia ben Joseph Al-Fayyumi; b. Egypt 882/892, d. Baghdad 942) was a prominent rabbi, Jewish philosopher, and exegete of the Geonic period who was active in the Abbasid Caliphate.