Nahshon bar Zadok was gaon of the academy of Sura for eight years in the second half of the ninth century. The precise chronology is in question, but his incumbency began between 865 and 871. His patronymic is also uncertain; it is given as Isaac in some versions of the Epistle of Sherira Gaon.

Nahshon wrote many responsa, including one explaining the proper usages of magic. He also wrote commentaries on several tractates of the Talmud, as well as a monograph explaining difficult words therein, and has been misidentified as the author of Sefer Re'u Ma, a ninth-century work on ritual slaughter.

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