Muhammad ibn Hasan al-Mahdi is believed by the Twelver Shia to be the last of the Twelve Imams and the eschatological Mahdi, who will emerge in the end of time to establish peace and justice and redeem Islam.

Twelver Shīʿism, also known as Imāmiyya, is the largest branch of Shīʿa Islam, comprising about 85 percent of all Shīʿa Muslims. The term Twelver refers to its adherents' belief in twelve divinely ordained leaders, known as the Twelve Imams, and their belief that the last Imam, Imam al-Mahdi, lives in Occultation and will reappear as the promised Mahdi.