Back to the Future Part III is a 1990 American science fiction Western film and the third installment of the Back to the Future trilogy. The film was directed by Robert Zemeckis, and stars Michael J. Fox, Christopher Lloyd, Mary Steenburgen, Thomas F. Wilson, and Lea Thompson. The film continues immediately following Back to the Future Part II (1989); while stranded in 1955 during his time travel adventures, Marty McFly (Fox) discovers that his friend Dr. Emmett "Doc" Brown (Lloyd), trapped in 1885, was killed by Buford "Mad Dog" Tannen (Wilson), Biff's great-grandfather. Marty travels to 1885 to rescue Doc and return once again to 1985, but matters are complicated when Doc falls in love with Clara Clayton (Steenburgen).

The Western is a film genre defined by the American Film Institute as films which are "set in the American West that [embody] the spirit, the struggle, and the demise of the new frontier." Generally set in the American frontier between the California Gold Rush of 1849 and the closing of the frontier in 1890, the genre also includes many examples of stories set in locations outside the frontier – including Northern Mexico, the Northwestern United States, Alaska, and Western Canada – as well as stories that take place before 1849 and after 1890. Western films comprise part of the larger Western genre, which encompasses literature, music, television, and plastic arts.