The phrase constitutional theocracy describes a form of elected government in which one single religion is granted an authoritative central role in the legal and political system. In contrast to a pure theocracy, power resides in lay political figures operating within the bounds of a constitution, rather than in the religious leadership.

The phrase was used in connection with the Iranian government of Ayatollah Khomeini in 1987 by Olivier Roy, and from the 1990s onward has been used in discussions of Iran, and occasionally of other governments. Professor Mahmood Mamdani has spoken of a "constitutional theocracy" in the context of "a state–wide clerical authority in Iran". Ran Hirschl of the University of Toronto law school has written more than one article discussing "constitutional theocracies": for example considering "modern states formally governed by principles of Islamic Shari'a laws".

The concept of constitutional theocracy is also used by journalists writing about Iran, or about the process of developing a constitution in Iraq, and in general discussions of the relationship between religion and government. Following its link with Iran's Islamic revolution, the phrase has also been used to discuss, among other topics, early twentieth-century Turkish politics and contemporary Chechnyan politics.