What do you call a person who is in charge of a monestry?

A person in charge of a monastery is typically called an "abbot" if male, or "abbess" if female. The abbot or abbess oversees the spiritual and administrative aspects of the monastery, guiding the community of monks or nuns. In some cases, other titles like "prior" or "priest" may also be used, depending on the specific religious order and its hierarchy.