KHᾹRIJĪS are the "third party" in Islam, who anathematize both the majority Sunnīs and the Shīʿī partisans of ʿAlī. Although few in number today, the Khārijīs played a role of great importance in the history of Muslim theology and political theory.

Their origins lie in the agreement between the fourth caliph, ʿAlī, and his challenger, Muʿāwiyah, kinsman and avenger of the murdered third caliph, ʿUthmān, to submit their quarrel to arbitration, following the Battle of Ṣiffīn (AH 37/657 CE). A group of ʿAlī's followers, at first mostly from the Arab tribe of Tamīm, held that ʿAlī had, by agreeing to treat with rebels, committed a great sin and could no longer be considered a Muslim. They made an exodus (khurūj) from his camp and collected at Ḥarūr...