Cujo (1981 (1981 in literature)) is a psychological horror novel by Stephen King. The novel won the British Fantasy Award in 1982, and was made into a film of the same name (Cujo (film)) in 1983.

The story focuses on the Trenton family: Vic, an advertisement designer, his adulterous wife Donna, and their four-year-old son Tad. The latter two are terrorized by the eponymous Cujo, a rabid (rabies) St. Bernard (St. Bernard (dog)). The narrative takes place in the authors recurrent fictional town of Castle Rock (Castle Rock (Stephen King)), Maine, and is interspersed with vignettes from the seemingly mundane lives of other residents. There are no official chapters, but rather breaks in between passages, which indicate when the author is alternating to a different point of view.

Cujo also references Kings previous novel, The Dead Zone (The Dead Zone (novel)), on several occasions. For instance, serial killer Frank Dodd has now achieved a kind of bogeyman status in Castle Rock.

Cujos name was based on the nom de guerre of Willie Wolfe, one of the men responsible for orchestrating Patty Hearsts kidnapping and indoctrination into the Symbionese Liberation Army.

Stephen King mentions Cujo in On Writing, referring to it as a novel he "barely remembers writing at all". The book was written during a period when King was drinking heavily. Somewhat wistfully, King goes on to say that he likes the book and that he wishes he could remember enjoying the good parts as he put them down on the page.