Ja'far ibn Yahya Barmaki, Jafar al-Barmak (767–803) is the son of a Bactrian vizier (Yahya ibn Khalid) of the Arab Abbasid caliph Harun al-Rashid and from whom he inherits that position.

He is a member of the influential Barmakids family.

He is beheaded in 803 for allegedly having an affair with Harun al-Rashid's sister Abassa, although historical sources remain unclear about the real cause of Jafar's death and the fall of the Barmakids.