director; head; superintendent; curator; chief librarian
The person in charge of a public or private facility (館). The exact English title depends on the type of facility: museum director/curator, library director/chief librarian, hall manager, etc.
He was appointed director of the National Museum.
I proposed the purchase of new books to the chief librarian.
She has served as the director of this museum for ten years.
He is scheduled to be appointed the new director next month.