MUBASHSHIR BEN RAV KIMOI HA-KOHEN (d. 925), Gaon of the Pumbedita Academy from 917 to 925, a post to which he was appointed upon the death of R. Judah Gaon (the grandfather of R. *Sherira Gaon). Mubashshir belonged to the faction which opposed the appointment of *David b. Zakkai as exilarch, apparently because of his family relationship with Mar *Ukba, the deposed exilarch. In turn, when David b. Zakkai did become exilarch, he refused to recognize Mubashshir in his post and appointed R. *Kohen Ẓedek as head of the Pumbedita Academy; the members of the Academy were split into two factions, each supporting one of the two geonim. A prominent supporter of Mubashshir was *Ben Meir, the gaon of Ereẓ Israel, who conducted an active campaign against both David b. Zakkai and R. Kohen Ẓedek. Saadiah Gaon, on the other hand, when he came to Baghdad in 921, joined Mubashshir's opponents. Mubashshir appointed R. Aaron b. Joseph *Sarjado as rosh kallah Pumbedita, in spite of his not being the scion of a scholarly family. In 922 David b. Zakkai made peace with Mubashshir and most of the members of the Academy accepted the latter's leadership; R. Kohen Ẓedek, and the few members who remained loyal to him, left the Academy but continued to receive their share of its income. None of Mubashshir's teachings and responsa has been preserved. On Mubashshir's death in 925 his rival R. Kohen Ẓedek succeeded him as gaon.
B.M. Lewin (ed.), Iggeret Sherira Ga'on (1921), 119–20; Mann, in: Tarbiz, 5 (1933/34), 150–8; Abramson, Merkazim, 21–23.