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.
Professor Hirschl has expanded on the distinction between constitutional theocracies and ordinary democracies in his article, 'Constitutional Courts vs. Religious Fundamentalism: Three Middle Eastern Tales. where he says:
The original text of Article 2 of the 1971 Egyptian Constitution read: 'Islam is the religion of the State, Arabic is its official language, and the principles of Islamic Shari’a are a principal source of legislation.' On May 22, 1980, the text of Article 2 was changed to read, 'Islam is the religion of the State, Arabic is its official language, and the principles of Islamic Shari’a are the principal source of legislation.' The result of this amendment effectively transformed Egypt into a 'constitutional theocracy,' in which no legislation could contravene Islamic legal principles.
Hirschl refers to the existence of official, government-established Shari’a courts in both Egypt and Iran as evidence that these are constitutional theocracies. Though his definition seems generally compatible with other views that a constitutional theocracy is a government using a single religion as its sole source of law, other writers do not mention Egypt as often as Iran in this context.
The lack of any official, government-established Shari'a courts in Iraq, and the use of the phrase "a principal source of legislation" rather than "the principal source of legislation" in the Iraqi constitution, has been understood to mean that Iraq is not a constitutional theocracy, at least according to Hirschl's definition.
- Translated summary of Roy's article La Théocratie Constitutionnelle cited in International Bibliography of the Social Sciences 1987
- Mahmood Mamdani: Herbert Lehman Professor of Government in the Departments of Anthropology and International Affairs, and Director of the Institute of African Studies at Columbia University
- Nermeen Shaikh, Good Muslim, Bad Muslim AsiaSource Interview with Mahmood Mamdani, May 2004 "Until Ayatollah Khomeini created a state–wide clerical authority in Iran, there was no such institutionalized religious hierarchy in Islam and it still does not exist elsewhere. Without the existence of an institutionalized religious hierarchy parallel to a state hierarchy, the question of the proper relation between two domains of power, that of the organized church and the organized state, a central question in Western secularism, has been a non–question in Islam – at least until Ayatollah Khomeini created a constitutional theocracy in Iran as vilayat–i–faqih."
- Ran Hirschl, Constitutionalism, Judicial Review, and Progressive Change Texas Law Review, Dec 2005, Vol. 84 Issue 2, p471-507 "the crucial role of courts in constitutional theocracies such as Egypt in determining the nature of public life in modern states formally governed by principles of Islamic Shari'a laws"
- Thomas Omestad, Wrestling with Tehran U.S. News & World Report; 03/02/98, Vol. 124 Issue 8, p44 "[the Iranian] Islamic republic, the world's only constitutional theocracy"
- Time 24 November 2003, Vol. 162 Issue 21, p36-44 "an Iranian-style constitutional theocracy"
- Hale, William M (1994). Turkish Politics and the Military. Routledge.
- VA Tishkov, Life in a War-Torn Society (University of California 2004)