The Star Wars prequel trilogy, colloquially referred to as the prequels, is a series of epic space-opera films written and directed by George Lucas. It was produced by Lucasfilm Ltd. and distributed by 20th Century Fox. The trilogy was released from 1999 to 2005 and is set before the original Star Wars trilogy (1977–1983), chronologically making it the first act of the Skywalker Saga. Lucas had planned a prequel trilogy (as well as a sequel trilogy) before the release of the original film, but halted major Star Wars films beyond the original trilogy by 1981. When computer-generated imagery (CGI) had advanced to the level he wanted for the visual effects he wanted for subsequent films, Lucas revived plans for the prequels by the early 1990s. The trilogy marked Lucas's return to directing after the 22-year hiatus following the original Star Wars film in 1977, as well as a 16-year hiatus between the classic and prequel trilogies.

The trilogy consists of Episode I – The Phantom Menace (1999), Episode II – Attack of the Clones (2002), and Episode III – Revenge of the Sith (2005). The films follow the training of the powerful youth Anakin Skywalker as a Jedi under the tutelage of Jedi Masters Qui-Gon Jinn, Obi-Wan Kenobi and Yoda, his fall to the dark side of the Force and rebirth as Darth Vader. The trilogy also depicts the corruption of the Galactic Republic, the genocide of the Jedi Order, and the rise of the Empire under Palpatine (secretly the Sith Lord Darth Sidious). The first two films received mixed reviews, while the third's reception was more positive. All three enjoyed box-office success.

It's all based on backstories that I'd written setting up what the Jedi were, setting up what the Sith were, setting up what the Empire was, setting up what the Republic was, and how it all fits together. I spent a lot of time in developing those elements, and what each planet did, and why they did it the way they did. So I had all this material. A lot of the story elements were given. Early on, it was that Anakin had been more or less created by the midi-chlorians, and that the midi-chlorians had a very powerful relationship to the Whills [from the first draft of Star Wars], and the power of the Whills, and all that. I never really got a chance to explain the Whills part.

So a lot of the story of the prequels, I'd done already. And now I was just having to put it into a script and fill it in, kind of sew up some of the gaps that were in there. I'd already established that all Jedi had a mentor, with Obi-Wan and Luke, and the fact that that was a bigger issue – that's the way the Jedi actually worked. But it was also the way that the Sith worked. There's always the Sith Lord and then the apprentice.

Everybody said, "Oh, well, there was a war between the Jedi and the Sith." Well, that never happened. That's just made up by fans or somebody. What really happened is, the Sith ruled the universe for a while, 2,000 years ago. Each Sith has an apprentice, but the problem was, that each Sith Lord got to be powerful. And the Sith Lords would try to kill each other because they all wanted to be the most powerful. So in the end they killed each other off, and there wasn't anything left. So the idea is that when you have a Sith Lord, and he has an apprentice, the apprentice is always trying to recruit somebody to join him – because he's not strong enough, usually – so that he can kill his master.

According to original trilogy producer Gary Kurtz, loose plans for a prequel trilogy were developed during the outlining of the original two films. In 1980, Lucas confirmed that he had the nine-film series plotted, but due to the stress of producing the original trilogy and pressure from his wife Marcia Lucas to settle down, he had decided to cancel further sequels by 1981. However, technical advances in the late 1980s and early 1990s, including the ability to create computer-generated imagery (CGI), inspired Lucas to consider that it might be possible to revisit his saga. In 1989, Lucas stated that the prequel trilogy would be "unbelievably expensive." After viewing an early CGI test created by Industrial Light & Magic for Jurassic Park, Lucas said:

We did a test for Steven Spielberg, and when we put them up on the screen I had tears in my eyes. It was like one of those moments in history, like the invention of the lightbulb or the first telephone call. A major gap had been crossed and things were never going to be the same.

In 1992, Lucas acknowledged that he had plans to create the prequel trilogy in the Lucasfilm Fan Club magazine, and announced this to Variety in late 1993. Producer Rick McCallum reached out to Frank Darabont, who had previously written The Young Indiana Jones Chronicles and The Shawshank Redemption, for possible future writing duties. He was considered until at least 1995, but as time went on, Lucas continued writing the screenplays himself. Jeffrey Boam, who had previously written Indiana Jones and the Last Crusade for Lucas, was interested in 1995 to rewrite and polish Lucas' scripts for the prequels. Before Lucas chose to direct the prequels, Return of the Jedi director Richard Marquand expressed interest in directing one of the prequel films, up until his death in 1987. The popularity of the franchise had been prolonged by the Star Wars Expanded Universe, so that it still had a large audience. A theatrical rerelease of the original trilogy in 1997 'updated' the 20-year-old films with the style of CGI envisioned for the new episodes.