Gershom ben Judah, (c. 960 -1040) best known as Rabbeinu Gershom (רבנו גרשום, "Our teacher Gershom") and also commonly known to scholars of Judaism by the title Rabbeinu Gershom Me'Or Hagolah ("Our teacher Gershom the light of the exile"), was a famous Talmudist and Halakhist.
Less than a century after Gershom's death Rashi said of him, "all members of the Ashkenazi diaspora are students of his." As early as the 14th century, Asher ben Jehiel wrote that Rabbeinu Gershom's writings were "such permanent fixtures that they may well have been handed down on Mount Sinai."
He is most famous for the synod he called around 1000 CE, in which he instituted various laws and bans, including prohibiting polygamy, requiring the consent of both parties to a divorce, modifying the rules concerning those who became apostates under compulsion, and prohibiting the opening of correspondence addressed to someone else.
Born in Metz in 960, Gershom was a student of Yehuda HaKohen be