Cujo is a horror novel by Stephen King, published by Viking in 1981. The book tells the story of the middle-class Trenton family and rural Camber clan in Castle Rock, Maine. Marital and financial difficulties of the mundane sort plague disgraced advertising man Vic Trenton and his adulterous wife Donna. Their domestic problems are dwarfed by the mortal danger when Donna and her four-year-old son Tad are terrorized by a rabid St. Bernard named Cujo. The novel was adapted into a 1983 film of the same name.
The book is a semi-sequel to King's earlier work The Dead Zone. The book makes several specific references to the events and characters. Even so much to lead the audience to believe that Frank Dodd (killed in The Dead Zone) is possessing Cujo. King made later reference to the dog in his 1983 novel Pet Sematary, in which a character briefly alludes to "a big old St. Bernard (that) went rabid downstate a couple of years ago and killed four people", a clear allusion to the events of Cujo, and in his later novel Needful Things.
Due to the popularity of King's novel and the subsequent film adaptation, the name of "Cujo" has since entered the realm of popular culture as a generic term or sarcastic insult in reference to a psychotic, violent, or imbalanced dog. It also is the nickname given to National Hockey League goalie Curtis Joseph, whose customized goalie masks feature drawings of ravenous dogs.
In his semi-biographical book On Writing, King said he wrote the book during the peak of a period of drug and alcohol abuse. He wrote that he remembered very little of writing Cujo as a result, one of his great regrets.