Sunni vs. Shia Muslims: The Difference Explained

Islam is the world’s second-largest religion. Pew Research Center counted about 2 billion Muslims in 2020, roughly a quarter of the world’s population. Nearly all of them belong to one of two main branches: Sunni Islam and Shia Islam. Both branches share the same core beliefs, but they split early in Islamic history over a question of leadership, and that split still shapes religious practice and politics in the Middle East today.

This explainer covers where the divide came from, how the two branches differ in authority and practice, where each group lives, and why the split comes up in news about Iran, Iraq, Saudi Arabia, Lebanon and the wider region.

What Sunni and Shia Muslims Share

Sunni and Shia Muslims believe in one God, accept Muhammad as the final prophet and treat the Quran as the word of God. Both follow the Five Pillars of Islam: the declaration of faith, the five daily prayers, almsgiving, fasting during Ramadan and the pilgrimage to Mecca. Both celebrate Eid al-Fitr and Eid al-Adha. Pew’s 2012 survey of Muslims in 39 countries found broad agreement across the branches on these basics, including belief in God and in Muhammad as his prophet.

How the Split Began

The divide goes back to the death of Muhammad in 632 CE and the question of who should lead the Muslim community after him.

• The Sunni position: the community could choose its leader, called a caliph. Early Muslims selected Abu Bakr, a close companion of Muhammad and the father of his wife Aisha, as the first caliph. The name Sunni comes from ahl al-sunna, “people of the tradition.”
• The Shia position: leadership should have passed within the Prophet’s family, to Ali ibn Abi Talib, Muhammad’s cousin and son-in-law. The name comes from Shiat Ali, “the party of Ali.”

Ali did become the fourth caliph in 656, but his rule was contested and he was assassinated in 661. The decisive moment for Shia identity came in 680 at the Battle of Karbala, in present-day Iraq, where Ali’s son Husayn and a small band of followers were killed by the forces of the Umayyad caliph Yazid. As the BBC’s explainer on the schism notes, Husayn’s death became the central story of sacrifice and mourning in Shia tradition.

Religious Authority

Sunni Islam has no single religious hierarchy. Authority rests with scholars and with four main schools of law, the Hanafi, Maliki, Shafii and Hanbali schools, which interpret the Quran and the sayings and practices of Muhammad (the hadith).

Shia Islam centers on the Imams, a line of leaders descended from Ali whom Shia Muslims regard as divinely guided. The largest Shia branch, Twelver Shiism, holds that the twelfth Imam went into hiding in the ninth century and will return. In his absence, senior clerics, including those known as ayatollahs, guide believers, and ordinary Shia Muslims typically follow a chosen senior cleric on matters of religious law. Smaller Shia branches include the Ismailis and the Zaydis, the group to which Yemen’s Houthi movement traces its roots.

Differences in Practice

• Prayer: both pray five times a day, but many Shia Muslims combine some prayers into three sessions. Postures differ slightly; many Shia worshippers pray with arms at their sides and rest their forehead on a small clay tablet.
• Ashura: Shia Muslims mark the anniversary of Karbala on the 10th of Muharram with mourning processions and passion plays. Many Sunnis also observe Ashura, usually as a day of fasting.
• Shrines and pilgrimage: Shia Muslims make pilgrimages to shrines of the Imams, especially Karbala and Najaf in Iraq and Mashhad in Iran. The Arbaeen pilgrimage to Karbala draws millions of people each year.
• Hadith collections: each branch relies on its own collections of the Prophet’s sayings and its own chains of transmitters.

Where Sunni and Shia Muslims Live

Pew’s global population study estimated that 87% to 90% of Muslims are Sunni and 10% to 13% are Shia. Pew found that between 68% and 80% of Shia Muslims live in just four countries: Iran, Pakistan, India and Iraq. Shia Muslims are a majority in Iran, Iraq, Azerbaijan and Bahrain, and form large communities in Lebanon, Yemen, Kuwait and Saudi Arabia’s Eastern Province. Sunni Muslims are the majority in most other Muslim-majority countries, including Indonesia, Pakistan, Bangladesh, Egypt, Turkey and Saudi Arabia. Pew cautions that the Sunni and Shia figures are less precise than the totals for Muslims overall.

Why the Divide Matters in Geopolitics

The Council on Foreign Relations describes the Sunni-Shia split as a fault line that political leaders have often used to build alliances and rally support. Iran, the largest Shia-majority state, became a theocracy after its 1979 revolution and backs Shia-led or Shia-aligned groups such as Hezbollah in Lebanon and militias in Iraq. Saudi Arabia, home to Islam’s holiest sites in Mecca and Medina, presents itself as a leader of the Sunni world. The rivalry between the two states has played out in Iraq after 2003, in Syria’s civil war, in Bahrain and in Yemen.

Analysts generally stress that these conflicts are driven by power, territory, money and national interest as much as by religion, and that Sunni and Shia Muslims live side by side and intermarry in many countries. For current coverage of the region, see our Iran War Tracker, the latest Iran-U.S. war update, our report on Lebanon-Israel talks and the Geopolitics hub.

Key Facts at a Glance

• Origin of the split: succession after Muhammad’s death in 632 CE.
• Sunni share of Muslims: about 87% to 90% (Pew).
• Shia share of Muslims: about 10% to 13% (Pew).
• Shia-majority countries: Iran, Iraq, Azerbaijan, Bahrain.
• Defining event for Shia Islam: the Battle of Karbala, 680 CE.

More from our World Affairs and Religion coverage.

Sources

• Pew Research Center: Mapping the Global Muslim Population
• Pew Research Center: How the Global Religious Landscape Changed From 2010 to 2020
• Pew Research Center: The World’s Muslims: Unity and Diversity
• BBC News: Sunnis and Shia: Islam’s ancient schism
• Council on Foreign Relations: The Sunni-Shia Divide