A monarch is the sovereign head of state in a monarchy. A monarch may exercise the most and highest authority in the state or others may wield that power on behalf of the monarch. Typically a monarch either personally inherits the lawful right to exercise the state's sovereign rights (often referred to as the throne or the crown) or is selected by an established process from a family or cohort eligible to provide the nation's monarch. Alternatively, an individual may become monarch by conquest, acclamation or a combination of means. A monarch usually reigns for life or until abdication. If a young child is crowned the monarch, a Regent is often appointed to govern until the monarch reaches the requisite adult age to rule. Monarchs' actual powers vary from one monarchy to another and in different eras; on one extreme, they may be autocrats (absolute monarchy) wielding genuine sovereignty; on the other they may be ceremonial heads of state who exercise little or no power or only reserve powers, with actual authority vested in a parliament or other body (constitutional monarchy).

Monarch, in the US often written Monarch!, is a French drone doom band.