Khomeinism or Khumaynism refers to the religious and political ideas of the leader of the Islamic Revolution, Ruhollah Khomeini. Khomeinism may also refer to the ideology of the clerical class which has ruled Iran since 1979. It can also be used to refer to the radicalization of segments of the Twelver Shia populations of Iran, Iraq, and Lebanon, and the Iranian government's recruitment of Shia minorities in Afghanistan, Pakistan, Saudi Arabia and Africa. The word Khomeinist and Khomeinists, derived from Khomeinism, are also used to describe members of Iran's clerical rulers and differentiate them from regular 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 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 landscape of Shia Islam; which traditionally upheld political quietism over a thousand years. Another significant revision 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 waiting patiently for His return, but Khomeini and his followers called upon Shia Muslims to actively pave the way for Mahdi's global Islamic rule.
Since his death, politics in the legal sphere of the Islamic Republic of Iran has been "largely defined by attempts to claim Khomeini's legacy", according to at least one scholar, and "staying faithful to his ideology has been the litmus test for all political activity" there.
According to Vali Nasr, outside Iran, Khomeini's influence has been felt among the large Shia populations of Iraq and Lebanon.