Imam Ayatollah Seyed Ruhollah Musavi Khomeini (May 17, 1900 – June 3, 1989) was a Muslim cleric and Marja, and the political leader of the 1979 Islamic Revolution of Iran which overthrew Mohammad Reza Pahlavi, the last Shah of Iran. Following the Revolution, Imam Khomeini became Grand Leader of Iran — the paramount figure in the political system of the new Islamic Republic — until his demise.
Imam Khomeini was considered a Marja-e taqlid to many Muslims, and in Iran was officially addressed as Imam rather than Grand Ayatollah; his supporters adhere to this convention. Imam Khomeini was also a highly-influential and innovative Islamic political theorist, most noted for his development of the theory of velayat-e faqih, the "guardianship of the jurisconsult."
Although during this scholarly phase of his life Imam Khomeini was not politically active, the nature of his studies, teachings, and writings revealed that he firmly believed from the beginning in political activism by clerics. Three factors support this suggestion. First, his interest in Islamic studies surpassed the bounds of traditional subjects of Islamic law (Sharia), jurisprudence (Fiqh), and principles (Usul) and the like. He was keenly interested in philosophy and ethics. Second, his teaching focused often on the overriding relevance of religion to practical social and political issues of the day. Third, he was the first Iranian cleric to try to refute the outspoken advocacy of secularism in the 1940s. His now well-known book, Kashf-e Asrar (Discovery of Secrets) was a point by point refutation of Asrar-e Hezar Saleh (Secrets of a Thousand Years), a tract written by a disciple of Iran's leading anti-clerical historian, Ahmad Kasravi. Also he went from Qom to Tehran to listen to Ayatollah Hassan Modarres —the leader of the opposition majority in Iran's parliament during 1920s.
Imam Khomeini became a Marja in 1963, following the death of Grand Ayatollah Seyyed Hossein Borujerdi.
In this time he could represent his religious-political ideas openly. Because the deaths of the leading, although quiescent, Shia religious leader, Ayatollah Seyyed Mohammad Borujerdi (1961), and of the activist cleric Ayatollah Abol-Ghasem Kashani (1962) left the arena of leadership open to Imam Khomeini, who had attained a prominent religious standing by the age of 60. In addition, although ever since the rise of Reza Shah Pahlavi to power in the 1920s the clerical class had been on the defensive because of his secular and anticlerical policies and those of his son, Mohammad Reza Shah, these policies reached their peak in the early 1960s with "White Revolution."
Only two weeks after the Shah fled Iran on January 16, 1979, Imam Khomeini returned from exile to Iran triumphantly, on Thursday, February 1, 1979, invited by the anti-Shah revolution which was already in progress.