The Iranian Revolution, also known as the Islamic Revolution, culminated in the overthrow of the Pahlavi dynasty in 1979. The revolution led to the replacement of the Imperial State of Iran by the Islamic Republic of Iran, as the monarchical government of Shah Mohammad Reza Pahlavi was superseded by Ruhollah Khomeini, an Islamist cleric who had headed one of the rebel factions. The ousting of Mohammad Reza Pahlavi, the last Shah of Iran, formally marked the end of Iran's historical monarchy.