Under Capricorn is a 1949 British historical drama film directed by Alfred Hitchcock about a couple in Australia who started out as lady and stable boy in Ireland, and who are now bound together by a horrible secret. The film is based on the play by John Colton and Margaret Linden, which in turn is based on the novel Under Capricorn (1937) by Helen Simpson. The screenplay was written by James Bridie from an adaptation by Hume Cronyn. This was Hitchcock's second film in Technicolor, and like his preceding color film Rope (1948), it features 9- and 10-minute long takes.

The film is set in colonial Sydney, New South Wales, Australia during the early 19th century. Under Capricorn is one of several Hitchcock films that are not typical thrillers: instead it is a mystery involving a love triangle. Although the film is not exactly a murder mystery, it does feature a previous killing, a "wrong man" scenario, a sinister housekeeper, class conflict, and very high levels of emotional tension, both on the surface and underneath.

The title Under Capricorn refers to the Tropic of Capricorn, which bisects Australia. Capricornus is a constellation; Capricorn is an astrological sign associated with the goat.