What are the differences between Sunni and Shia Muslims? These two major traditions of Islam share the Quran, belief in one God, recognition of Muhammad as a prophet, and the principal religious obligations of Muslims. Their distinction stems first from the history of the succession to the Prophet, who died in 632, and then from differing conceptions of religious authority. Over the centuries, this separation also gave rise to distinctive theological, legal, and ritual traditions. They are therefore not really two separate religions, but two major branches within Islam.
When Muhammad died, the Muslim community had to decide who would lead it. Abu Bakr, a companion and father-in-law of the Prophet, became the first caliph. The traditions that would give rise to Sunni Islam recognize the legitimacy of his succession, followed by those of Umar and Uthman. Other believers considered that Ali ibn Abi Talib, Muhammad’s cousin and son-in-law, should succeed him because of his family and spiritual closeness to the Prophet. They gradually formed the movement known by the Arabic expression shi‘at Ali, “the party of Ali,” from which the term Shia Islam derives.
It would, however, be anachronistic to imagine two fully formed religious denominations already existing in 632. Sunni and Shia identities developed gradually through political conflicts, religious debates, and the transmission of different traditions. Ali himself became the fourth caliph in 656, before being assassinated in 661. The question of the legitimacy of his descendants then took on growing importance for his supporters. The history of this division, as recounted notably by the Council on Foreign Relations, thus goes beyond a disagreement over the choice of a successor.
One event left a lasting mark on Shia memory: in 680, Husayn, Ali’s son and Muhammad’s grandson, was killed with several of his relatives at the Battle of Karbala, in present-day Iraq, by forces of the Umayyad rulers (the caliphate led by the Umayyad dynasty, which ruled the Muslim world from Damascus from 661 to 750. The first hereditary dynasty of caliphs, it succeeded the first four caliphs of Islam). His death became a symbol of faithfulness to justice and resistance to oppression. It occupies a central place in Shia commemorations of Ashura, the tenth day of the month of Muharram. Ashura is also observed among Sunnis, but its meaning and observances differ, notably through the practice of fasting in certain traditions.
The most fundamental doctrinal difference concerns authority. In Sunni Islam, religious teaching is based on the Quran, the Prophetic tradition, the study of hadiths, and the work of scholars and jurists. No single leader is recognized by all Sunnis as the infallible spiritual heir of the Prophet. The term “imam” refers in particular to the person who leads prayers, but can also be applied to great scholars. Schools of Islamic law developed recognized methods for interpreting the sources and formulating religious rules.
In much of Shia Islam, by contrast, the notion of the imamate grants particular religious authority to Ali and to a line of imams descended from the Prophet’s family. For Twelver Shia Muslims, who make up the principal branch of Shia Islam, twelve imams succeeded one another; the twelfth is believed to have entered occultation and is awaited for his return. This belief should not be extended to every Shia tradition, which differ over the number of imams and the continuity of their authority. Nevertheless, it explains an essential part of Twelver Shia religious identity.
Neither branch constitutes a uniform whole. Sunni Islam comprises four major classical schools of Islamic law: Hanafi, Maliki, Shafi‘i, and Hanbali. Shia Islam includes, notably, Twelvers, Ismailis, and Zaydis, whose conceptions of the imamate and religious traditions differ.
The sources of the Prophetic tradition are another area of distinction. Sunnis and Shias recognize the importance of words and actions attributed to Muhammad, but their collections of hadiths and their criteria for transmission are not identical. Shia traditions give particular importance to teachings passed down by the imams of the Prophet’s family. This difference can influence interpretations of religious law, understandings of certain historical events, and devotional practices. It does not imply a general disagreement over the fundamental texts of Islam, which remain largely shared.
Everyday religious life mainly shows differences in form. The five obligatory daily prayers are recognized in both traditions, but many Twelver Shias combine them into three periods of the day, whereas customary Sunni practice distributes them over five distinct prayer times. The position of the hands during prayer, certain formulas, or the use of a small clay tablet during prostration may also differ. These practices are neither identical in every community nor sufficient, on their own, to determine a believer’s religious affiliation.
Holy places also illustrate the shared heritage and the distinctive features of each tradition. Mecca and Medina occupy a fundamental place for all Muslims. Shrines associated with Ali and Husayn, notably in Najaf and Karbala, also hold particular importance for Shias. The pilgrimages and gatherings held there express devotion to the Prophet’s family. Both branches also contain diverse spiritual traditions, including certain forms of Sufism, and ways of living one’s religion that vary greatly from one society to another.
In demographic terms, Sunnis represent the large majority of Muslims. In its 2009 global study, the Pew Research Center estimated that they accounted for between 87% and 90% of Muslims, compared with 10% to 13% for Shias. These are historical estimates that are regularly cited, not a new count established in 2026. Shia Islam is the majority tradition or has a particularly significant presence in Iran, Iraq, Azerbaijan, and Bahrain, and has substantial communities in Pakistan, India, Lebanon, and Yemen. Sunni and Shia populations also live side by side in many countries.
The religious map does not simply coincide with political borders. Iran is predominantly Shia, while Saudi Arabia is predominantly Sunni, but rivalries between states cannot be reduced to doctrinal differences. Power relationships, economic interests, national policies, and regional conflicts also play decisive roles. Conversely, relations between Sunnis and Shias often take the form of ordinary coexistence, family ties, intellectual exchanges, or dialogue initiatives, which receive less attention in accounts focused on crises.
Understanding the differences between Sunnis and Shias therefore requires considering both their shared heritage and the developments specific to each. The succession to Muhammad was the historical starting point of a division that deepened around the authority of the imams, legal interpretations, and certain practices. But both traditions recognize the foundations of Muslim faith and belong to closely intertwined religious histories. For further reading, the entries in the Simple Dictionary of Religions devoted to Sunni Islam and Shia Islam introduce each of these traditions separately.
Featured image: The Hassan Tower and the columns of the former mosque in Rabat. Archival photograph illustrating the city. Photo: Carlos ZGZ / Wikimedia Commons, CC0.