Kharijites (Arabic kharawrij,”the leavers”), earliest Muslim sect, originally among the supporters of Ali, the fourth caliph of Islam (see Caliphate). Ali outraged the Kharijites, however, when he allowed his claim to the caliphate to be arbitrated by his followers and by the partisans of Muawiyah I. The Kharijites claimed that God (Allah) had decreed Ali's caliphate and therefore arbitration by mortals was sacrilegious. Thereafter, they repudiated not only Ali and Muawiyah but all Muslims who did not accept their views.

According to Kharijite doctrine, not only descendants of the Prophet Muhammad and members of the Muslim aristocracy but anyone—even a slave—could become a caliph if morally and religiously pure. A caliph, to be legitimate (in accord with God's will), had to be elected as the free choice of the entire Muslim community. An unsatisfactory caliph could be deposed or put to death. The Kharijites, both extremely pious and puritanical in religious practice and theory, also accepted only a literal interpretation of the sacred Qur'an (Koran). They developed their own laws and collections of Hadith—the Traditions, or Muhammad's actions and utterances witnessed by his companions and transmitted by reliable authorities.

Today about 500,000 Kharijites, usually referred to as Ibadites, survive, dwelling in North and East Africa, Oman, and Zanzibar (now part of Tanzania). Their puritanism and idealism have greatly influenced the present-day Wahhabi movement, which includes the majority of Saudi Arabians.