The original Star Wars trilogy, formerly marketed as the Star Wars Trilogy (and colloquially referred to as the 'original trilogy' or classic trilogy), is the first set of three films produced in the Star Wars franchise, an American space opera created by George Lucas. It was produced by Lucasfilm and distributed by 20th Century Fox, and consists of Star Wars (1977), The Empire Strikes Back (1980) and Return of the Jedi (1983). Beginning in medias res, the original trilogy serves as the second act of the nine-episode Skywalker Saga. It was followed by a prequel trilogy between 1999 and 2005, and a sequel trilogy between 2015 and 2019. Collectively, they are referred to as the "Skywalker Saga" to distinguish them from spin-off films set within the same universe.

The films center on the Galactic Civil War between the Rebel Alliance and the tyrannical Galactic Empire, as well as the archetypical hero's journey of Luke Skywalker in his quest to become a Jedi under the tutelage of exiled Jedi Masters Obi-Wan Kenobi and Yoda. Luke joins forces with Princess Leia, Han Solo, Chewbacca, C-3PO, R2-D2 and the Rebel Alliance in facing the Empire and the evil Sith Lord Darth Vader.

The original Star Wars film received widespread acclaim from critics for its storytelling, characters, John Williams' musical score and its groundbreaking visual and sound effects. The film surpassed 1975's Jaws as the highest grossing film of all time, turning science fiction films into a blockbuster genre, until it was surpassed by E.T. the Extra-Terrestrial in 1982. Star Wars and The Empire Strikes Back have been hailed as among the greatest and most important films of all time. Since the original trilogy's release and success, Star Wars has become a pop culture phenomenon, spawning a multimedia franchise, consisting of countless TV series, video games, books and theme park attractions, complete with a multi-million dollar merchandising empire. All three films have been inducted by the Library of Congress for preservation in the United States National Film Registry for being "culturally, historically, or aesthetically significant".

In 1971, Lucas wanted to film an adaptation of the Flash Gordon serial, but could not obtain the rights. He began developing his own story inspired by the work of Edgar Rice Burroughs. Immediately after directing American Graffiti (1973), Lucas wrote a two-page synopsis for his space opera, titled Journal of the Whills. After United Artists, Universal Studios and Disney rejected the film, 20th Century Fox decided to invest in it. Lucas felt his original story was too difficult to understand, so on April 17, 1973, he began writing a 13-page script titled The Star Wars, sharing strong similarities with Akira Kurosawa's The Hidden Fortress (1958). By May 1974, he had expanded the script into the first draft of a screenplay, adding elements such as the Sith and the Death Star, but found that the script had grown too long for a single film. Subsequent drafts evolved into the script of the original film.

Lucas negotiated to retain the sequel rights. Tom Pollock, then Lucas's lawyer, writes: "We came to an agreement that George would retain the sequel rights. Not all the [merchandising rights] that came later, mind you; just the sequel rights. And Fox would get a first opportunity and last refusal right to make the movie." Lucas was offered $50,000 to write, another $50,000 to produce, and $50,000 to direct the film; his directing compensation was later increased to $100,000. He also negotiated the sequel rights and ownership of 40% of the merchandising profits. American Graffiti cast member Harrison Ford had given up on acting to try to become a carpenter, until Lucas hired him to play Han Solo.

During the development of the trilogy after the initial conception of the first film, Lucas took inspiration from Marvel Comics and the characters from the Marvel Universe who were popular in the 1970s to come up with many plot points and ideas for various designs.

Thousands of actors were assessed in the search for the trilogy's main cast. The selected actors are considered by many viewers to have onscreen chemistry even though some of them were inexperienced, with the notable exceptions of Alec Guinness and Peter Cushing. Some, like Ford, have called the dialogue in the scripts clunky, and several lines were unscripted; some of these are considered the most memorable moments in the films.

Star Wars was released on May 25, 1977; unlikely hero Luke Skywalker is drawn into a galactic conflict between the Empire and Rebel Alliance by two droids and an old Jedi Knight; he helps make one of the Rebellion's most significant victories. The film's unanticipated success led Lucas to make it the basis of an elaborate serial. With the backstory he created for the sequel, Lucas decided that the series would be a trilogy of trilogies, with the original film given the subtitle Episode IV – A New Hope to establish it as the first part of the second trilogy. The first sequel, Star Wars: Episode V – The Empire Strikes Back, was released on May 21, 1980, and sees Luke begin training as a Jedi under the last living Jedi master, Yoda. Luke confronts Sith Lord Darth Vader, who is revealed to be Luke's father. Vader attempts to convert Luke to the dark side of the Force. The third film, Episode VI – Return of the Jedi, was released on May 25, 1983, and follows Luke as a full-fledged Jedi. Luke succeeds in redeeming Vader, thereby saving the galaxy from the Empire. The sequels were self-financed by Lucasfilm, and generally advertised without the episodic number distinction present in their opening crawls.