The Iranian Revolution, culminating in 1979, marked a pivotal change in Iran's political landscape, leading to the overthrow of the Pahlavi dynasty and the establishment of the Islamic Republic of Iran. This transition ended the monarchical rule of Pahlavi and ushered in the theocratic government led by Ayatollah Ruhollah Khomeini.^[94] The ousting of Pahlavi, the last Shah of Iran, formally marked the end of Iran's historical monarchy.^[95]

Post-1953 coup, Pahlavi aligned Iran with the Western Bloc, particularly the United States, to strengthen his authoritarian rule. For 26 years, he maintained Iran's position away from Soviet influence.^[96] The Shah's modernization efforts, known as the White Revolution, began in 1963, which led to the exile of Khomeini, a vocal opponent of Pahlavi's policies. However, ideological tensions between Pahlavi and Khomeini persisted, leading to widespread anti-government demonstrations starting in October 1977.^[97]

The Cinema Rex fire in August 1978, where hundreds died, became a catalyst for a broader revolutionary movement.^[98] Pahlavi left Iran in January 1979, and Khomeini returned from exile in February, greeted by several thousands of supporters.^[99] By 11 February 1979, the monarchy collapsed, and Khomeini assumed control.^[100] Following the March 1979 Islamic Republic referendum, in which 98% of Iranian voters approved the country's shift to an Islamic republic, the new government began efforts to draft the present-day Constitution of the Islamic Republic of Iran;^[101] Ayatollah Khomeini emerged as the Supreme Leader of Iran in December 1979.^[102]

The success of the Iranian Revolution in 1979 was met with global surprise due to its unique characteristics. Unlike typical revolutions, it did not stem from defeat in war, a financial crisis, peasant uprisings, or military dissatisfaction. Instead, it occurred in a country experiencing relative prosperity and brought about rapid, profound changes. The revolution was massively popular and led to a significant exile, forming a large part of today's Iranian diaspora.^[103] It replaced Iran's pro-Western secular and authoritarian monarchy with an anti-Western Islamist theocracy. This new regime was based on the concept of Velâyat-e Faqih (Guardianship of the Islamic Jurist), a form of governance straddling authoritarianism and totalitarianism.^[104]

The revolution set forth a core ideological objective of destroying the Israeli state^[105] and sought to undermine Sunni influence in the region. It supported the political ascendancy of Shi'ites and exported Khomeinist doctrines internationally.Following the consolidation of Khomeinist factions, Iran began to back Shia militancy across the region to combat Sunni influence and establish Iranian dominance, aiming for an Iranian-led Shia political order.