regent

noun
1
a person who rules a country because the king or queen is too young, old, ill, etc.
نایب‌السلطنه, قیم سلطنت, سرپرست سلطنت
adjective
1
used after a noun such as prince or queen to show that the prince or queen is ruling a country because the real king or queen is too young, old, ill, etc.
نایب‌السلطنه