Muhammad ibn Ali al-Hadi was the son of Ali al-Hadi and the brother of Hasan al-Askari, the 10th and 11th Twelver Shia Imams respectively.
A section of the Imamate Shiites believed that the Awaited Imam Mahdi was Muhammad ibn Ali al-Hadi, who died suddenly in Dajil. They believed in his occultation, like that claimed for Isma'il ibn Jafar, and they did not believe in his death. This sect was known as the Muhammadite Shia.