Shia Islam is the second-largest branch of Islam. It holds that the Islamic prophet Muhammad PBUH designated ʿAlī ibn Abī Ṭālib (656–661 CE) as his successor (khalīfa) and the Imam (spiritual and political leader) after him, most notably at the event of Ghadir Khumm, but was prevented from succeeding prophet Muhammad PBUH as the leader of the Muslims as a result of the choice made by some of Muhammad's PBUH other companions (ṣaḥāba) at Saqifah. This view primarily contrasts with that of Sunnī Islam, whose adherents believe that prophet Muhammad PBUH did not appoint a successor before his death and consider Abū Bakr, who was appointed caliph by a group of Muhammad's PBUH other companions at Saqifah, to be the first rightful (rāshidūn) caliph after prophet Muhammad PBUH (632–634 CE). Adherents of Shīʿa Islam are called Shia Muslims.
