Prince regent

George IV of the United Kingdom, as prince regent, while his father was mentally incapable between 1811 and 1820. By Henry Bone.

A prince regent or princess regent is a prince or princess who, due to their position in the line of succession, rules a monarchy as regent in the stead of a monarch, e.g., as a result of the sovereign's incapacity (minority or illness) or absence (e.g., by remoteness, such as exile or long voyage, or the absence of an incumbent).

While the term itself can have the generic meaning and refer to any prince or princess who fills the role of regent, historically it has mainly been used to describe a small number of individual princes and princesses who were regents of non-principalities.