Aaron ben Moses ben Asher was a Jewish scholar from Tiberias, famous as the most authoritative of the Tiberian Masoretes, and a member of a family who had been involved in creating and maintaining the Masoretic Text (authoritative text of the Hebrew scripture), for at least five generations.
His Sefer Diqduqei HaTe'amim ("Grammar of the Punctuation/Vocalizations") was an original collection of grammatical rules and Masoretic information.