Nahshon ben Zadok Gaon (Hebrew: נחשון בן צדוק or sometimes: Nahshon b. Zadok) was head of the Academy of Sura from 874 to 882, in succession to Mar Amram ben Sheshna.
This erroneous notion is known as, and is contained in, the Iggul [Cycle] di R. Nahshon, which work was printed with the She'erit Yosef of Joseph b. Shem-Ṭob b. Joshua (1521).
Nahshon and his son Hai Gaon did not approve of saying the "Kol Nidre" on the eve of Yom Kippur.
Most of his responsa, contained in the collection Sha'are Ẓedeḳ, are written in Aramaic in a curt, difficult style; but the responsa ascribed to him in Teshubot Ge'onim Ḳadmonim are written in mixed Hebrew in a plain, easy diction.
Some of his decisions conflict with the Talmud, and in his haggadic interpretations he did not always agree with the older haggadists.