A monarch is the head of a monarchy, a form of government in which a state is ruled by an individual who normally rules for life or until abdication, and typically inherits the throne by birth. Monarchs may be autocrats (as in all absolute monarchies) or may be ceremonial figureheads, exercising only limited or no reserve powers at all, with actual authority vested in a legislature and/or executive cabinet (as in many constitutional monarchies). In many cases, a monarch will also be linked with a state religion. Most states only have a single monarch at any given time, although a regent may rule when the monarch is a minor, not present, or otherwise incapable of ruling. Cases in which two monarchs rule simultaneously over a single state, as is the current situation in Andorra, are known as coregencies.
A variety of titles are applied in English; for example, "king" and "queen", "prince" and "princess", "grand duke" and "grand duchess", "emperor" and "empress". Although they will be addressed differently in their local languages, the names and titles in the list below have been styled using the common English equivalent. Roman numerals, used to distinguish related rulers with the same name, have been applied where typical.
