Alī ibn Abī Ṭālib cousin and son-in-law of Muhammad, the Prophet of Islam

ʿAlī, in full ʿAlī ibn Abī Ṭālib, (born c. 600, Mecca, Arabia [now in Saudi Arabia]—died January 661, Kufa, Iraq), cousin and son-in-law of Muhammad, the Prophet of Islam, and fourth of the “rightly guided” (rāshidūn) caliphs, as the first four successors of Muhammad are called. Reigning from 656 to 661, he was the first imam (leader) of Shiʿism in all its forms. The question of his right to the caliphate (the political-religious structure comprising the community of Muslims and its territories that emerged after the death of Muhammad) resulted in the only major split in Islam, into the Sunni and Shiʿi branches.