Coregencies

Coregencies, or co-regencies, describe political arrangements in which two or more individuals exercise sovereign authority simultaneously or in overlapping terms. In a formal coregency, co-rulers share legal legitimacy and public power; in a transitional or junior coregency, a ruler with a designated successor governs jointly, often while the successor is still a minor or being trained.

Coregencies arise for reasons of dynastic continuity, political stabilization, or managing disputed succession. They can be formalized by royal decree or regnal charter, or emerge through practice when a reigning monarch and heir rule together for a period.

Historically, coregencies have appeared in various political contexts. In ancient Egypt, a ruler could share power with an heir, a pattern seen in the case of Hatshepsut and Thutmose III; similar arrangements occurred within the Ptolemaic and other Hellenistic kingdoms. In the late Roman and early Byzantine periods, emperors sometimes designated co-emperors to govern different halves of the realm or to ensure a smooth transition, producing a form of coregency. The Diocletian–Maximian diarchy, while not always described as a coregency, established parallel imperial authority that influenced later practice.

In modern constitutional monarchies, co-regency is rare and typically resolved through formal succession laws rather than sustained joint sovereignty. The enduring legacy of coregencies lies in their attempt to balance dynastic legitimacy with political stability, especially during periods of transition or crisis.