JOSEPH, king of the *Khazars. As his correspondence with *Ḥisdai ibn Shaprut demonstrates, he ruled in the tenth century. In the heading of his presumed reply to Ḥisdai's letter, the Reply of Joseph, he is called "the Togarmian [i.e., Turkish] king" (cf. Gen. 10:3), and in the text of the Reply is referred to as Joseph b. Aaron b. Benjamin. His descent is traced back to *Obadiah, king of the Khazars. In the fragment known as the Cambridge Document, which was found in the Cairo Genizah, his father Aaron and grandfather Benjamin are also mentioned by name and the document adds (line 59) that Joseph was married to a daughter of the king of the Alans.
Dunlop, Khazars, index; A.N. Poliak, Kazaryah (19513), index.