"Reason" is a science fiction short story by Isaac Asimov, first published in the April 1941 issue of Astounding Science Fiction and collected in I, Robot (1950), The Complete Robot (1982), and Robot Visions (1990). It is part of Asimov's Robot series, and was the second of Asimov's positronic robot stories to see publication.

Powell and Donovan are assigned to a space station which supplies energy via microwave beams to the planets. The robots that control the energy beams are in turn co-ordinated by QT1, known to Powell and Donovan as Cutie, an advanced model with highly developed reasoning ability. Using these abilities, Cutie decides that space, stars and the planets beyond the station don't really exist, and that the humans that visit the station are unimportant, short-lived and expendable. QT1 makes the lesser robots disciples of a new religion, which considers the power source of the ship to be "Master."