A caliphate is the Islamic form of government representing the political unity and leadership of the Muslim world. The head of state's position (Caliph) is based on the notion of a successor to the Islamic prophet Muhammad's political authority.
The Sunni branch of Islam stipulates that, as a head of state, a Caliph should be elected by Muslims or their representatives. Followers of Shia Islam, however, believe a Caliph should be an Imam chosen by Allah from the Ahl al-Bayt (the "Family of the House", Muhammad's direct descendants).
As of this writing, the Ottoman Dynasty is the last substantial caliphate. From 1517 to 1922, the Sultan of the Ottoman Empire was also the Caliph. The Ottoman Caliphate was abolished in 1924, two years after the downfall of the Empire. A number of minor caliphates have appeared since then, but they have been typically limited in recognition and in influence on the Muslim world. The Islamic State of Iraq and Syria, also known as the Caliphate, has had a substantial impact in the areas it was has seized since 2013, but has no recognition outside of its domain, and is actively opposed by a substantial coalition.
Caliphate in "Islands in the Sea"Edit
Under the Umayyads, the Caliphate grew rapidly geographically. Islamic rule expanded westward across North Africa and into Hispania, and eastward through Persia and ultimately to Sindh and Punjab. Its crowning achievement was the conquest of the Roman Empire and the fall of Constantinople.
Other Caliphs play roles in the works of Harry Turtledove. Caliphs who died before a given story's point of divergence may be referenced. Stories set in OTL may reference past Caliphs, or even the sitting Caliph, but unless there are speculative elements attached to their roles in the story, they do not belong in this list.