Caliph, also qualified as an Arab, khalīfah (“successor”), ruler of the Muslim community. When Prophet Muhammad died (June 8, 632), Abū Bakr succeeded to his political and administrative functions as khalīfah rasūl Allāh, “successor of the Messenger of God”, but he was probably under ‘Umar ibn al-Khaṭṭāb, the second caliph. The term caliph came into use as a title for the civil and religious head of the Muslim state. In the same sense, the term was used in the Qur’an in reference to both Adam and David as the vice rulers of God.

Abū Bakr and his three immediate successors are known as the “perfect” or “correctly guided” caliphs (al-khulafā’ al-rāshidun). After them, the title was borne by the 14 Umayyad caliphs of Damascus and later by the 38′ Abbāsid caliphs of Baghdad, whose dynasty fell to the Mongols in 1258. There were titular caliphs of ‘Abbāsid descent in Cairo under the Mamluks from 1258 until 1517, when the last caliph was captured by the Ottoman sultan Selim I. The Ottoman sultans then claimed the title and used it until it was abolished by the Turkish Republic on March 3, 1924.

After the fall of the Umayyad dynasty in Damascus (750), the title of caliph was also assumed by the Spanish branch of the family that ruled in Spain at Córdoba (755-1031), and was also assumed by the Fāṭimid rulers of Egypt. (909-1171), who claimed descent from Fāṭimah (daughter of Muhammad) and her husband, ‘Ali.

According to the Shī’ites, who call the supreme office the “imamate”, or leadership, no caliph is legitimate unless he is a lineal descendant of the Prophet Muhammad. The Sunnis insist that the office belongs to the Quraysh (Koreish) tribe, to which Muhammad himself belonged, but this condition would have vitiated the claim of the Turkish sultans, who held the office after the last Abbāsid caliph of El Cairo transferred it to Selim ME.

Some of the early caliphs were; Abu Bakr (632–634), Umar I (634–644), Uthman ibn Affan (644–656), Ali (656–661), Muʿawiyah I (661–680), Abd al-Malik (685–705), al-Walid (705–715), Hisham (724–743), Marwan II (744–750).