The Librarian of Unseen University is a character in Terry Pratchett's Discworld series of fantasy novels.

The Librarian is known for his violent reaction whenever he hears anyone refer to him as a monkey (orang-utans are apes). He speaks an elaborate language whose vocabulary consists of the single word Ook (and its antonym eek - where ook means yes, eek tends to mean no). Nonetheless, most people seem to be able to understand him. Both his language and his reaction were used separately and together as jokes in the first Discworld game.