For many people, the difference between Sunni and Shia Muslims can feel confusing, but it actually begins with a very simple historical question: Who should have led the Muslim community after the Prophet Muhammad died in 632 CE?

Sunni Muslims believed leadership should be chosen by the community, and they supported Abu Bakr, a close companion of Muhammad. Shia Muslims believed leadership should stay within the Prophet’s family, beginning with Ali, his cousin and son‑in‑law. What started as a political disagreement eventually grew into two distinct traditions with their own practices, scholarship, and spiritual leadership structures.

Over time, Sunnis developed a system where no single leader holds divine authority. Instead, religious understanding comes from scholars and four major schools of interpretation. Shia Muslims, especially the Twelver branch, believe in a line of Imams—descendants of Ali—who carry spiritual guidance and authority. These differences shape how each community approaches religious leadership, law, and devotion, even though both share the same core beliefs about God, the Qur’an, and the Prophet Muhammad.

Today, Sunni Muslims make up the vast majority of the global Muslim population—about 85 to 90 percent. Shia Muslims represent roughly 10 to 15 percent worldwide, forming significant communities in places like Iraq, Lebanon, Bahrain, and Pakistan.

The most notable Shia‑majority nation is Iran, where about 90 percent of the population follows Twelver Shi’ism. This identity became central to Iran’s culture and religious life beginning in the 16th century under the Safavid dynasty.

Coming next: What is “Twelver Shi’ism”?