List of current reigning monarchs by length of reign

This is a list of currently reigning monarchs sorted by length of service.

This list includes monarchs who do not reign over entire nations, such as Muhammad V of Kelantan, but does not include former monarchs and pretenders, such as Simeon II of Bulgaria, ex officio monarchs such as Emmanuel Macron who in his capacity as President of France is also Co-Prince of Andorra, monarchs without physical territories such as the Prince and Grand Master of the Sovereign Military Order of Malta, constituent monarchs such as the traditional African rulers, or monarchs whose position is unofficial, such as Tenzin Gyatso, 14th Dalai Lama.

Hassanal Bolkiah is currently the longest-reigning monarch, having been Sultan of Brunei since 5 October 1967. He became the longest-reigning monarch upon the death of Elizabeth II of the United Kingdom on 8 September 2022.