Khomeinism, also transliterated Khumaynism, refers to the religious and political ideas and practices connected with the leader of the 1979 Iranian Islamic Revolution – Ruhollah Khomeini. While primarily referring to the ideas and practices of Khomeini himself, Khomeinism may also refer to the ideology of the clerical class which has ruled the Islamic Republic of Iran founded by Khomeini, following his death, and to the "radicalization" of segments of the Twelver Shia populations of Iran, Iraq, and Lebanon, and to the Iranian government's "recruitment" of Shia minorities in Afghanistan, Pakistan, Saudi Arabia, and Africa. The words Khomeinist and Khomeinists, derived from Khomeinism, can also be used to describe members of Iran's clerical rulers as opposed to "regular" (non-Wilayat ul-Faqih supporting) Shia Muslim clerics.
Under Khomeini's leadership, Iran replaced its millennia-old monarchy with a theocratic republic. Khomeini brought about a major paradigm shift in Shia Islam. He declared that Islamic jurists (clerics specializing in Islamic jurisprudence) are the true holders of religious and political authority, who must be obeyed as "an expression of obedience to God", and whose rule has "precedence over all secondary ordinances in Islam such as prayer, fasting, and pilgrimage". Khomeini's doctrines would make a major influence on the landscape of Shia Islam; which had upheld political quietism for over a thousand years. Another significant revision of tradition was on Mahdism, the messianic belief in the reappearance of their Twelfth Imam and the proper way to wait for Him. Traditional Twelver theologians urged believers to wait patiently for his return, but Khomeini and his followers called upon Shia Muslims to actively pave the way for Mahdi's global Islamic rule.