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 serves as regent in the stead of a monarch who is a minor, incapacitated, or otherwise absent, whether by remoteness, such as exile or a long voyage, or the absence of an incumbent. The term may be used generically for any prince or princess acting in such a capacity, but historically it has been applied most prominently to certain regents in European monarchies.