Monday Begins on Saturday () is a 1965 science fantasy novel by Soviet writers Boris and Arkady Strugatsky, with illustrations by Yevgeniy Migunov. Set in a fictional town in northern Russia, where research in magic occurs, the novel is a satire of Soviet scientific research institutes. It offers an idealistic view of the scientific work ethic, as reflected in the title which suggests that the scientists' weekends are nonexistent. Their idealism is contrasted by an inept administration and a dishonest, show-horse professor.

The "Scientific Research Institute of Sorcery and Wizardry" (or, in Andrew Bromfield's 2002 translation "the National Institute for the Technology of Witchcraft and Thaumaturgy", abbreviated to "NITWITT"), located in the fictional Northern Russian town of Solovets, is portrayed as a place where everyone either works diligently, or else their loss of honesty is symbolized by their ears becoming more and more hairy. These hairy-eared people are viewed with disdain by the idealistic scientists. The more morally backward specimens are the most self-aggrandizing and sure of their own significance, while conducting the more ridiculous and nonsensical pseudo-research, to justify their position.

Monday Begins on Saturday

Tale of the Troika, which describes Soviet bureaucracy at its worst, is a sequel, featuring many of the same characters.

Monday Begins on Saturday

Characters and events

The novel is written from the point of view of Aleksandr Ivanovich Privalov (usually called Sasha), a young programmer from Leningrad, who picks up two hitchhikers during a road trip north through Karelia. After the two find out that he is a programmer, they convince him to stay in Solovets and work together with them in the Scientific Research Institute of Sorcery and Wizardry (abbreviated NIIChaVo in Russian, which sounds very close to "Ничего", the word for "nothing").

Monday Begins on Saturday

The book contains a large number of references to well-known Russian fairy tales and children's stories: Baba Yaga makes an appearance as do Zmey Gorynych and the Learned Cat from Pushkin's "Ruslan and Lyudmila", who turns out to be a slightly demented bard. Some figures from lore and history also appear, such as genies and Cain. The authors portray these persons and concepts (such as magic) either as objects of scientific inquiry or members of the institute. Merlin, for example, is described as an incompetent boaster and is in charge of the institute's Department of Predictions. The Technical Helpdesk is headed by one Sabaoth Baalovich Odin, also described as the most powerful wizard in the universe, while the vivarium is staffed by Alfred, a vampire.

The novel is remarkable for its colorful characters. For example, Cristóbal Josevich Junta was formerly a Grand Inquisitor, and is now the head of the Department of the Meaning of Life. He is also a talented taxidermist. It is rumored that his collection includes a Standartenführer of the SS, an erstwhile friend of Junta's and also a taxidermist. Cristóbal Josevich, so goes the rumor, was equally skilled, only faster. Fyodor Simeonovich Kivrin, the head of the Department of Linear Happiness, is a stuttering big guy, an eternal optimist, an apprentice programmer, a fan of Erle Stanley Gardner, and a mentor of sorts to Privalov. Modest Matveevich Kamnoedov (whose surname translates to "stone-eater") is an archetypal administrator and bureaucrat who does not understand the "Monday begins on Saturday" work ethic. On New Year's Eve, he directs Privalov to turn off the lights and lock all doors, but Privalov soon finds out that everyone is still at the Institute and research continues. For example, the archetypically rude Viktor Korneev (usually called Vitka) claims to have left his clone to work in his lab, which Privalov recognizes to be Korneev himself, because clones never sing or show any emotion.