Maṣliaḥ ben Solomon ha-Cohen (Hebrew: מצליח בן שלמה הכהן, Arabic: ابو منصور صالح بن سليمان الهاروني, Abū Manṣūr Ṣāliḥ bin Sulaymān al-Hārūnī;[1] died 1139), alternatively Matzliach, was a Gaon and the leader of the Palestinian Gaonate in Fustat, the principal Talmudic academy and central legalistic body of the Jewish community in Palestine.

Masliah was a son of the previous Gaon, Solomon ben Elijah ha-Cohen, part of the Priestly family that had ruled the Palestinian Gaonate since the middle of the 11th century.

[6] Masliah originally studied in the Palestinian Gaonate under his father in Damascus; a Genizah fragment mentions he attained the rank of "the Fourth" in the administration of the Yeshiva.

[2] His influence extended beyond Egypt; a query was sent to him from Yemen concerning the status of Chinese porcelain,[10] and a manumission document for an Indian slave was written under his authority in Mangalore, India in 1132.

[15] Israeli Talmudic scholar Yehudah Seewald has identified and published several of Masliah's sermons found in the Cairo Genizah, including for the Jewish holidays of Purim,[16] Passover,[17] Shavuot,[18] and Yom Kippur.