- "In a real Scare, you do not want to get caught by a kid's parent. And in this event, you do not want to get caught by...the librarian."
- —Brock Pearson warning his group about the Librarian
The Librarian is an elderly female monster who works at Monsters University's school library, and a minor antagonist.
She hates noises inside the library. If she catches any monster being too loud, she will attack the offending party with her tentacles, and anyone who gets caught will be tossed out of the library and into a pond facing the entrance. The librarian is involved in the "Avoid The Parent" course of the Scare Games, the librarian's reaction to noise is exploited to emulate the danger of parents, and how a Scarer has to get along without being caught by one. Any team who is caught by her is thrown out of the library and disqualified from the competition. The only way you can be disqualified if you get caught, not if you just make a noise.
When Oozma Kappa accidentally make a creak in the library's floorboards, grabbing the Librarian's attention, they all start scattering and purposely make sounds from different parts of the library, therefore confusing and distracting the librarian while Squishy takes their flag unnoticed, and ultimately causing her to capture Slugma Slugma Kappa and toss them out of her library and into the pond instead.
The Librarian appears to be quiet yet very grouchy, and immediately tries to get rid of anyone who makes noise in the library.
The librarian resembles a tiny gray cephalopod monster with eight tentacles, gray hair, and wears a black dress and horn-rimmed glasses. Although she seems to be small and inoffensive when sitting at her desk, she turns out to be a lumbering giant about the same size as the library in which she works when she stands.
- The librarian also bears some resemblance to Ursula, the villainess of the 1989 Disney animated film The Little Mermaid. They both have octopus-like tentacles, and they are both elderly looking. However, Ursula has six tentacles while the librarian has the accurate number of eight.
- Although the librarian's real name was not told of in the movie, in the Monsters University Fearbook, her name is said to be Margaret Gesner.
- The Librarian isn’t really an antagonist, but seems that way because she attacks any monster who makes too much noise in the library.
- The Librarian has similarities to the Pale Man from Pan's Labyrinth, because the hero has to sneak past her to get something. Her eyesight may be failing, but she knows when intruders enter her territory and captures them. Whereas the Pale Man devours children who step into his lair, the Librarian captures noisy students and throws them out of the library because it's her job.