The Constitution of the Islamic Republic of Iran was ratified on October 24, 1979, effectively ending the Iranian Revolution. It replaced the former constitution which had been in effect since 1906. The constitution establishes Iran as an Islamic Republic and defines Shia Islam as the country's official religion.

Under the Iranian constitution, the appointed "supreme leader," the Ayatollah Ali Khamenei is the highest ranking political and religious authority in the nation. The Ayatollah acts as Commander in Chief of the armed forces, dictates domestic and foreign policy and appoints six of the twelve members of the Council of Guardians, which oversees Parliamentary activities. The elected leaders, including President Mahmoud Ahmadinejad, are subordinate to the Supreme Leader. Iran is the only country in which the armed forces are not controlled by the government's executive branch.