noun
chief librarian; head librarian
Refers to the director or head of a library, typically a public or university library.
彼女は国立図書館の図書館長に任命された。
She was appointed chief librarian of the National Library.
司書 is a general librarian, while 図書館長 is the head or director of a library.
Compound of 図書館 (library) and 長 (head, chief).