According to the 2011 Iranian census, 99.38% of Iranians believe in Islam, while 0.2% of the population believe in officially recognized minority religions, Christianity, Judaism and Zoroastrianism.
Muslims believe in one God. “God” in Arabic, the language of the Qur’an, is Allah. Muslims also follow the teachings of God’s prophets, the last of whom was Muhammad. After Prophet Muhammad’s death in 632 A.D., two main branches of Islam developed: Shi’i and Sunni. The Shi’is believed that the leadership of Islam was passed down to Muhammad’s descendants through his cousin and son-inlaw, Ali. The Sunnis believed that the true leaders were those elected from among Muhammad’s closest followers.
Over the centuries, other differences in beliefs and Sunna, or codes of behavior, developed between Shi’is and Sunnis. A branch of Shi’i Islam, called Jafari, or Twelver, Shi’i Islam is based on the belief that Prophet Muhammad’s twelfth and final descendant, who disappeared in the 800s, never died. Twelver Shia believe that he has been in hiding, and will return one day to lead the people.