Back to the Future Part II is a 1989 American science fiction film directed by Robert Zemeckis from a screenplay by Bob Gale; both wrote the story. It is a sequel to the 1985 film Back to the Future and the second installment in the Back to the Future franchise. The film stars Michael J. Fox, Christopher Lloyd, Lea Thompson and Thomas F. Wilson, with Elisabeth Shue (replacing Claudia Wells) and Jeffrey Weissman (replacing Crispin Glover) in supporting roles. It follows Marty McFly (Fox) and his friend Doctor Emmett "Doc" Brown (Lloyd) as they travel from 1985 to 2015 to prevent the former's son from tarnishing their family's future. When their arch-nemesis Biff Tannen (Wilson) steals the DeLorean time machine and uses it to alter history for his benefit, the duo must return to 1955 to set things right.

The film was produced on a $40 million budget and was filmed back to back with its sequel Part III. Filming began in February 1989, after two years were spent building the sets and writing the scripts. Back to the Future Part II was also a ground-breaking project for visual effects studio Industrial Light & Magic (ILM). In addition to digital compositing, ILM used the VistaGlide motion control camera system, which allowed an actor to portray multiple characters simultaneously on-screen without sacrificing camera movement.

Back to the Future Part II was released by Universal Pictures on November 22, 1989. Though the film received mostly positive reviews, it was deemed inferior to its predecessor by critics at the time of release. In the years since, the film has been reappraised and is now considered one of the best sequel and science fiction films of all time. The film grossed over $332 million worldwide in its initial run, making it the third-highest-grossing film of 1989. Part III followed on May 25, 1990, concluding the trilogy.