Halloween II is a 1981 American slasher film directed by Rick Rosenthal, in his directorial debut, written and produced by John Carpenter and Debra Hill, and starring Jamie Lee Curtis and Donald Pleasence, who reprise their respective roles as Laurie Strode and Dr. Sam Loomis. It is the second installment in the Halloween film series and serves as a direct sequel to Halloween (1978). The story picks up immediately after the cliffhanger ending of the first film, with Michael Myers following survivor Laurie Strode to the local hospital, while his psychiatrist Dr. Loomis continues his pursuit of him.

Though Carpenter and Hill co-wrote the screenplay to the sequel, Carpenter was reluctant to extend his involvement and mostly refused to direct, instead appointing the direction to Rosenthal. Filming took place in the spring of 1981, primarily at Morningside Hospital in Los Angeles, California, on a budget of $2.5 million. Stylistically, Halloween II reproduces certain key elements that made the original Halloween a success, such as first-person camera perspectives, and was intended to finish the story of Michael Myers and Laurie Strode. It also introduces the plot twist of Laurie Strode being the sister of Michael Myers, an element that would form the narrative arc of the series in subsequent films after Halloween II—including Rob Zombie's remake and its sequel—but was dropped from the current series' canon from the 2018 film onwards.

Halloween II was distributed by Universal Pictures, and premiered in the United States on October 30, 1981. The film received mixed reviews from critics and grossed $25 million domestically. A sequel with an unrelated story, titled Halloween III: Season of the Witch, was released in 1982. A direct sequel, Halloween 4: The Return of Michael Myers, was released in 1988. Another direct sequel, Halloween H20: 20 Years Later, was released in 1998, which acknowledges only the first two films.