Due to the [[ First Fitna]] which led to the sectarian division of [[Sunni Islam|Sunni]] vs. [[ Shia Islam| Shia]] Islam, the [[ succession of Muhammad]] is disputed within Islam.
The only two caliphs recognized in both Sunni and mainstream Shia Islam are [[ Ali|Ali ibn Abi Talib]] and [[Hasan ibn Ali]], considered the fourth and fifth or the first two, respectively. However the oldest sect of Shia Islam, the [[Zaidiyyah]] sect, does recognise the caliphate of the first two caliphs of Islam Abu bakr and Umar ibn al Khattab.
The [[Hadith of the Twelve Successors]] states that Muhammad that there will only be twelve caliphs, all of them from the [[Quraysh]] tribe, and that there would be impostor caliphs to guard against, and that after the last of the twelve caliphs, the earth will be swallowed.
Within Sunni Islam, there were universally recognized or "ecumenical" caliphs from the 7th century until the 13th- century [[ Siege of Baghdad (1258)|Mongol sack of Baghdad]], a period comprising the so-called [[ Islamic Golden Age]]. After the death of [[Al-Musta'sim]], last Abbasid Caliph in Baghdad , in 1258, there were no universally recognized caliphs until 1517, when Ottoman sultan [[Selim I]] induced [[Al-Mutawakkil III]] to formally surrender the title of caliph after [[ Ottoman–Mamluk War (1516–17)| defeating]] the [[Mamluk Sultanate ( Cairo)| Mamluk Sultanate]].
Afterwards, the Ottoman sultans also carried the title of caliph, until the declaration of [[Abdülmecid II]] as " ceremonial caliph" (1922–1924).
Since 1924, there have again been no caliphs with universal recognition within Sunni Islam.