coregency

thumb|right|Pharaoh Cleopatra VII and her eldest son and co-regent [[Ptolemy XV, carving on temple at Dendera|upright]]

A coregency is the situation where a monarchical position (such as prince, princess, king, queen, emperor or empress), normally held by only a single person, is held by two or more. It is distinct from diarchies or duumvirates (such as Andorra, ancient Sparta and Rome), where monarchical power is permanently divided between two rulers; and also from regencies, where a person, who is not legally monarch themselves, exercises monarchical power on the behalf of reigning monarch who is absent or unable to rule (for example due to illness or young age).