A monarchy is a form of government in which a person, the monarch, is head of state for life or until abdication. The political legitimacy and authority of the monarch may vary from restricted and largely symbolic, to fully autocratic, and can span across executive, legislative, and judicial domains.

A monarch is a head of state for life or until abdication, and therefore the head of state of a monarchy. A monarch may exercise the highest authority and power in the state, or others may wield that power on behalf of the monarch. Usually a monarch either personally inherits the lawful right to exercise the state's sovereign rights or is selected by an established process from a family or cohort eligible to provide the nation's monarch. Alternatively, an individual may proclaim oneself monarch, which may be backed and legitimated through acclamation, right of conquest or a combination of means.