Star Trek IV: The Voyage Home is a 1986 American science fiction film, the fourth installment in the Star Trek film franchise based on the television series Star Trek. The second film directed by Leonard Nimoy, it completes the story arc begun in Star Trek II: The Wrath of Khan (1982), and continued in Star Trek III: The Search for Spock (1984). Intent on returning home to Earth to face consequences for their actions in the previous film, the crew of the USS Enterprise finds the planet in grave danger from an alien probe attempting to contact now-extinct humpback whales. The crew travel to Earth's past to find whales who can answer the probe's call.

After directing The Search for Spock, Nimoy was asked to direct the next feature, and given greater freedom regarding the film's content. Nimoy and producer Harve Bennett conceived a story with an environmental message and no clear-cut villain. Dissatisfied with the first screenplay produced by Steve Meerson and Peter Krikes, Paramount hired The Wrath of Khan writer and director Nicholas Meyer. Meyer and Bennett divided the story between them and wrote different parts of the script, requiring approval from Nimoy, lead actor William Shatner, and executives at Paramount Pictures.

Principal photography commenced on February 24, 1986. Unlike previous Star Trek films, The Voyage Home was shot extensively on location, using many real settings and buildings for scenes set around and in the city of San Francisco. Special effects firm Industrial Light & Magic assisted in post-production and the film's special effects. Few of the humpback whales in the film were real. ILM devised full-size animatronics and small motorized models to stand in for the real creatures. The film was dedicated to the crew of the Space Shuttle Challenger, which broke up 73 seconds after takeoff on the morning of January 28, 1986.

The Voyage Home was released on November 26, 1986, in North America by Paramount Pictures, and became the top-grossing film at the weekend box office. The film's humor, acting, direction, special effects and unconventional story were well received by critics, fans of the series, and the general audience. It was financially successful, grossing $133 million worldwide, and earned several awards and four Academy Award nominations for cinematography and sound. It was followed by Star Trek V: The Final Frontier in 1989.