The Iranian Revolution, also known as the Islamic Revolution, saw the overthrow of the 2,500-year-old Persian monarchy under Mohammad Reza Shah Pahlavi and its replacement with an Islamic Republic led by Ayatollah Ruhollah Khomeini. The revolution was fueled by widespread resentment against the Shah's autocratic rule, Westernization policies, and perceived corruption. Following the Shah's departure into exile, Khomeini returned from France and established a theocratic government based on Islamic law. The event had a seismic impact on global politics, leading to the 444-day Iran Hostage Crisis with the U.S. and a major shift in the balance of power in the Middle East. It remains a unique example of a modern revolution that replaced a Western-backed secular monarchy with a conservative religious regime.