A caliphate is a state under the leadership of an Islamic steward with the title of caliph, a person considered a religious successor to the Islamic prophet Muhammad and a leader of the entire ummah (community). Historically, the caliphates were polities based in Islam which developed into multi-ethnic trans-national empires. During the medieval period, three major caliphates succeeded each other: the Rashidun Caliphate (632–661), the Umayyad Caliphate (661–750) and the Abbasid Caliphate (750–1258). In the fourth major caliphate, the Ottoman Caliphate, the rulers of the Ottoman Empire claimed caliphal authority from 1517. During the history of Islam, a few other Muslim states, almost all hereditary monarchies, have claimed to be caliphates.