Aaron ha-Cohen (Gaon)
Aaron ha-Cohen (Hebrew: אהרן הכהן)  was a head of the Palestinian Gaonate in the 10th century.

Details 

According to a fragment found in the Cairo Genizah (T-S 312.82), Aaron ha-Cohen reigned as Gaon after Abraham ben Aaron (the edge of the fragment is cut and does not allow for reconstruction of the length of his reign). It is possible that he is the Aaron ha-Cohen who wrote a calligraphic invitation to a certain elder Suwayd and his son to come to a lecture on the Sabbath.

This Aaron ha-Cohen should be distinguished from a different Aaron ha-Cohen who served under Joseph ben Ezrun ha-Cohen later in the 10th century.

References 

Geonim
10th-century rabbis