Eleventh imam of the Twelver (Ithna Ashari) Shiis. Born in Medina. Became the imam following the death of his father, Ali al-Hadi, in 868 and is believed to have left a son named Muhammad, the last imam of the Twelvers. Lived a life of strict seclusion and was kept under surveillance by the Abbasid caliph. Died in Samarra, Iraq, where he is buried beside his father.