Back to the Future Part III is a 1990 American science fiction Western comedy film, and the third and final installment of the Back to the Future trilogy. The film was directed by Robert Zemeckis and starred Michael J. Fox, Christopher Lloyd, Mary Steenburgen, Thomas F. Wilson, and Lea Thompson. The film continues immediately following Back to the Future Part II. While stranded in 1955 during his time travel adventures, Marty McFly (Fox) discovers that his friend Dr. Emmett "Doc" Brown, trapped in 1885, was killed by Biff Tannen's great-grandfather Buford. Marty decides to travel to 1885 to rescue Doc.
Back to the Future Part III was filmed in California and Arizona, and was produced on a $40 million budget back-to-back with Back to the Future Part II. Part III was released in the United States on May 25, 1990, six months after the previous installment. Part III earned $244.5 million worldwide against a budget of $40 million, making it the sixth-highest-grossing film of 1990.
On November 12, 1955, Marty McFly discovers that his friend, Dr. Emmett "Doc" Brown, had become trapped in 1885. Marty, with the 1955 Doc, uses the information in Doc's 1885 letter to locate and repair the DeLorean. He spots a tombstone with Doc's name, dated six days after the letter. Learning that Doc was killed by Biff Tannen's great-grandfather, Buford "Mad Dog" Tannen, Marty travels back to 1885 to save Doc.