Rav Sherira Gaon (Hebrew: רב שרירא גאון or R. Sherira ben Ḥanina Gaon, Hebrew: רב שרירא גאון בר חנינא or merely Sherira b. Ḥanina) was the head (gaon) of the Academy of Pumbeditha. He was one of the most prominent Geonim of his period, and the father of Hai Gaon, who succeeded him as gaon.
Sherira was born in 906 and died in 1006. (Rabinowich p. xx; see also Abraham ibn Daud i. 66-67).
He wrote the Iggeret Rav Sherira Gaon (" Epistle of Rav Sherira Gaon"), a comprehensive history of the composition of the Talmud. The Iggeret was an answer to an enquiry from Kairouan about the authorship and composition of the Mishnah and Talmud, and in particular why earlier authorities are seldom cited by name and the authorities that are so cited do not seem to be chronologically continuous.
The Iggeret exists in two recensions, a "French" and a "Spanish" recension. The "French" recension is in Aramaic, and is believed by many scholars to be the original version, though the contrary is strongly urged by Rabbi Israel Moses Hazan. The "Spanish" recension contains a higher proportion of Hebrew. The two recensions appear to differ on the question of whether the Mishnah was recorded in writing by Rabbi Judah haNasi. The Spanish recension definitely says that it was. The French recension appears to say that it was not, and this was the traditional view among Ashkenazi Jews. However, the notes to a recent edition of the French recension argue that the French wording is also consistent with the Mishnah having been written down.
Read more about Sherira Gaon: Life, His Responsa, His Circular Letter