Who is appointed to govern a state because the monarch is a minor, is absent or is incapacitated?

A regent is a person appointed to govern a state because the monarch is a minor, is absent or is incapacitated. The rule of a regent or regents is called a regency. A regent or regency council may be formed ad hoc or in accordance with a constitutional rule. Regent is sometimes a formal title. If the regent is holding his position due to his position in the line of succession, the compound term prince regent is often used; if the regent of a minor is his mother, she is often referred to as queen regent.

If the formally appointed regent is unavailable or cannot serve on a temporary basis, a regent ad interim may be appointed to fill the gap.

In a monarchy, a regent usually governs due to one of these reasons, but may also be elected to rule during the interregnum when the royal line has died out. This was the case in the Kingdom of Finland and the Kingdom of Hungary, where the royal line was considered extinct in the aftermath of World War I. In Iceland, the regent represented the King of Denmark as sovereign of Iceland until the country became a republic in 1944.