The Geonim (singular: Gaon, meaning ‘excellency’ or ‘genius’) are the heads of the two great Babylonian academies — Sura and Pumbedita — who serve as the supreme halakhic authorities for worldwide Jewry from approximately 589 to 1038 AD. Communities across the Jewish world sent questions (she’elot) to the Geonim and received authoritative responses (teshuvot), creating the first global network of Jewish legal authority. The Geonim standardized the prayer liturgy (Siddur Amram Gaon, ~860 AD), produced the first systematic halakhic codes (Halakhot Gedolot), and defended Talmudic Rabbinic Judaism against the Karaite challenge. The Gaonic period ends with the death of Hai Gaon (1038 AD) and the rise of independent rabbinic centers in North Africa and Europe.