A constitutional monarchy is a political system headed by a monarch. However, the monarch's power is not absolute. Instead, the king's or queen's powers, rights, duties, and responsibilities in the political system are limited by constitutional rules and principles, statutory laws, court decisions, and even customary rules of political behavior. Limits on the monarch's powers have generally evolved over time, and the modern monarch in a constitutional monarchy is essentially a figurehead who symbolizes national unity and often serves to rise above partisanship in the political system.

There are several constitutional monarchies in the world today. Of the member states of the European Union, seven are constitutional monarchies: Great Britain, Belgium, The Netherlands, Spain, Sweden, Denmark, and Liechtenstein. Japan remains a constitutional monarchy, albeit with a politically weak and largely ceremonial king, and several states in the British Commonwealth of Nations, such as Canada, Australia, New...