Back to the Future Part II is a 1989 film and the first sequel to the 1985 film Back to the Future. Like the previous film, it was directed by Robert Zemeckis and written by Zemeckis and Bob Gale. Part II and the third installment of the trilogy, Back to the Future Part III, were filmed back-to-back and released six months apart. Although released in 1989 and 1990, both films continued to portray 1985 as the present.

Part II follows the continued adventures of Marty McFly and "Doc" Emmett Brown as they use their time-traveling De Lorean, which is now capable of flight, to travel to a retro-futuristic version of 2015, an alternate 1985 and the principal setting of the first film in 1955. The film ends with a cliffhanger that is resolved in Part III.

Taking up where the previous film left off, Marty McFly, "Doc" Brown and Jennifer Parker arrive in 2015. Doc tranquilizes Jennifer, who is not necessary for his plan, explaining that he brought her along only because she saw the time machine. Doc explains that Marty's son is about to be approached by Griff Tannen, Biff's grandson, and his gang, who will ask him to take part in a robbery. According to Doc, this event leads to the ruin of the entire McFly family. Marty impersonates his future son and tells Griff he will not join the robbery, leading to a hoverboard chase that damages the nearby courthouse. Griff and his gang are arrested and the planned robbery never occurs.

Before meeting up with Doc, Marty notices a sports almanac in a store window which lists sports statistics through the year 2000. Imagining the potential for financial gain in 1985, Marty buys the book. Doc discovers the almanac and throws it away, chiding Marty for his plan. Meanwhile, Jennifer, still tranquilized, is found by the police, mistaken for her future self after thumbprint identification, and taken to her future home. Hiding in a closet, she witnesses the Marty of 2015 being fired from his job he is caught in an illegal scheme that his colleague, Douglas J. Needles, goaded him into joining. Doc finds Jennifer and sneaks her out of the house.

While Doc is rescuing Jennifer, the old-aged Biff of 2015 recovers the discarded sports almanac and steals the De Lorean. He returns the car to 2015 just as Marty and Doc prepare to leave for their own time. Upon arrival in 1985, Marty and Doc find that Hill Valley has become a dilapidated, crime-ridden slum lorded over by a middle-aged Biff, who is now immeasurably rich and powerful thanks to decades of successful sports betting. He has also married Marty's widowed mother, Lorraine, after secretly killing her husband George. Doc deduces that the Biff of 2015 must have given the almanac to his younger self sometime in the past. Marty confronts Biff and finds out that he received the almanac on November 12, 1955, the date on which the climax of the previous film took place.

Marty and Doc travel back to 1955 to prevent Biff from getting the almanac. Marty eventually manages to steal the book from the 1955 Biff and burns it, restoring history to its proper course. As Doc attempts to land the De Lorean to pick Marty up, the car is struck by lightning, causing it to disappear. A few seconds later a Western Union delivery man appears with a letter, which he explains was sent seventy years ago with the explicit instructions that it be delivered to Marty "at this exact location, at this exact minute, November 12, 1955." Marty tears open the letter, which is from Doc, explaining that he is now trapped in 1885. Marty runs to the clock tower to find the Doc of 1955, just as lighting strikes as depicted in Part I. Seeing Marty, who he has just sent back to 1985, Doc faints to a cliffhanger of "to be concluded..." appearing onscreen.

This is followed by a teaser trailer to Back to the Future Part III before the credits.

Back to the Future Part II earned $27 million in its first weekend of U.S. release (November 22, 1989) and $118 million total US gross – $332 million worldwide. However, this was still short of the first film's gross, and the film experienced a drop of over 50% in its second weekend, a steep figure at the time. The same fate occurred in Part III, which Universal Studios released only six months later. On December 17, 2002 the studio released all three movies in a three disc DVD and three tape VHS boxed set which sold extremely well when it was released, despite having widely discussed widescreen framing problems, which had led to a less widely publicized product recall.