Religion in Iran

Religion in Iran has been shaped by multiple religions and sects over the course of the country's history.

Zoroastrianism was the main followed religion during the Achaemenid Empire (550–330 BC), Parthian Empire (247 BC–224 AD), and Sasanian Empire (224–651 AD). Another Iranian religion known as Manichaeanism was present in Iran during this period. Jewish and Christian communities (the Church of the East) thrived, especially in the territories of northwestern, western, and southern Iran—mainly Caucasian Albania, Asoristan, Persian Armenia, and Caucasian Iberia. A significant number of Iranian people also adhered to Buddhism in what was then eastern Iran, such as the regions of Bactria and Sogdia.

Between 632–654 AD, the Rashidun Caliphate conquered Iran, and the next two centuries of Umayyad and Abbasid rule (as well as native Iranian rule during the Iranian Intermezzo) would see Iran, although initially resistant, gradually adopt Islam as the nation's predominant faith. Sunni Islam was the predominant form of Islam before the devastating Mongol conquest (1219–1221 AD), but with the advent of the Safavid Empire (1501–1736), Shi'ism became the predominant faith in Iran.

There have been a number of surveys on the current religious makeup of Iran. Those using telephone and face-to-face survey modes show a very high percentage of Iranian identifying as Muslim—99.98% in the official 2011 Iranian government census, whose numbers were used by the CIA World Factbook, and 96.6% in the World Values Survey in 2020. The CIA World Factbook estimated that in 2020 98.5% of the population adhered to Islam. Online social media-based surveys conducted by GAMAAN, which use chain referrals to self-select participants, reported that Shia Muslims constituted 32.2% of Iranians in 2020, 56% in February 2022, 37.5% in December 2022, and 37.9% in July 2023. The U.S. News & World Report placed Iran 3rd on the ranking of the most religious nations in 2024.

In 2024, Iran was scored zero out of four for religious freedom by Freedom House. Christianity, Judaism and Zoroastrianism are officially recognized and protected, and have reserved seats in the Iranian parliament. Iran is home to the second largest Jewish community in the Muslim world and the Middle East. The three largest non-Muslim religious minorities in Iran are the followers of the Baháʼí Faith, Christianity and Yarsanism. Sometime after 1844, the Baháʼí community became the largest religious minority group in Iran; they have been persecuted throughout their existence and are not recognized as a faith by the Iranian government.