A caliphate (from the Arabic خلافة or khilāfah), is a form of government the Islamic that developed in the first half millennium after the life of Muhammad. The post of caliph comprises of the unity of head of state, head of government, and head of religion, and represents the political unity and leadership of the Muslim world. The literal meaning of caliph is 'successor', as in, successor to Muhammad's political authority.
By the Sunni muslim view, he is ideally a member of the Quraysh tribe elected democratically by the majority of the Muslim population. According to the Shi'a, he is an Imam descended directly from the Ahl ul-Bayt. According to the Ibadi view, any Muslim who is just and righteous is fit to take the post.
The post of caliph has been held by the democratically elected Rashidun caliphs, and by the monarchist caliphates, successively the Umayyads, the Abbasids, and the Ottomans. In addition to these widely recognized caliphates, numerous local rulers assumed the title. The Fatimids of Egypt, who were the Imams of the Ismaili subdivision of the Shia, also used the title of caliph.
The Ottoman caliphate was declared abolished by the Turkish Parliament in 1924 following Mustafa Kemal's revolution in Turkey. Soon afterwards the King of hijaz, as guardian of the holy places, declared himself caliph. He was recognized outside his own kingdom by a few mosques in Iraq and Transjordan, but he was soon deposed by the Saudis, abdicating in favour of his son, who in turn renounced his claims. In 1926, a semi-official international congress declared the caliphate suspended. Since then, there have been various attempts to re-establish the caliphate, peacefully and violently. For example, Hizb ul-Taheri seeks the peaceful re-establishment of the caliphate, while al-Qaeda seeks to re-establish it through armed jihad. Currently, the closest generally recognized entity to the caliphate is the Organization of the Islamic Conference. In 2014 a group controlling substantial parts of Iraq and Syria proclaimed its leader Caliph, and he was also recognized in small areas of Libya and Nigeria.