A monarchy is a form of government where a single person, called a monarch, serves as the head of state, usually for their entire life. The most common types of monarchs are kings and queens, though some countries have emperors or sultans instead.

In most monarchies throughout history, the position passed from parent to child within a royal family. When a king or queen dies or steps down, their eldest child typically becomes the next monarch. This system of inheritance is called hereditary succession. The United Kingdom's current monarch, King Charles III, inherited the throne when his mother, Queen Elizabeth II, died in 2022.

Monarchies vary widely in how much power the ruler actually holds. In an absolute monarchy, the monarch controls the government with few or no limits on their authority. Saudi Arabia operates this way today, and France did before its revolution in 1789. In a constitutional monarchy, the monarch serves mainly as a ceremonial figurehead while elected officials run the government. The United Kingdom, Japan, Spain, and Sweden are modern constitutional monarchies where kings and queens attend ceremonies and represent their nations but don't make laws or control policy.

For most of human history, monarchy was the dominant form of government worldwide. Today, only about 40 countries still have monarchs, and most are constitutional monarchies where real power rests with elected leaders.