Sunni Islam is the largest branch of Islam, followed by 85–90% of the world's Muslims, and simultaneously the largest religious denomination in the world. Its name comes from the word Sunnah, referring to the tradition of Muhammad. The differences between Sunni and Shia Muslims arose from a disagreement over the succession to Muhammad and subsequently acquired broader political significance, as well as theological and juridical dimensions. According to Sunni traditions, Muhammad left no successor and the participants of the Saqifah event appointed Abu Bakr as the next-in-line. This contrasts with the Shia view, which holds that Muhammad appointed his son-in-law and cousin Ali ibn Abi Talib as his successor.

The Saqifa of the Banu Sa'ida clan refers to the location of an event in early Islam where some of the companions of the Islamic prophet Muhammad pledged their allegiance to Abu Bakr as the first caliph and successor to Muhammad shortly after his death in 11 AH. The Saqifa meeting is among the most controversial events in early Islam, due to the exclusion of a large number of Muhammad's companions, including his immediate family and notably Ali, his cousin and son-in-law. The conflicts that arose soon after Muhammad's death are considered to be the main cause of the current division among Muslims. Those who accepted Abu Bakr's caliphate were later labeled Sunnis, while the supporters of Ali's right to caliphate were later labeled Shia.