Alien 3 (stylized as Alien³) is a 1992 science-fiction thriller film and the debut feature film of director David Fincher. The film is the third installment of the Alien film series. The film takes place right after the events of Aliens (1986), an escape pod from the Colonial Marine spaceship Sulaco crash-lands on a prison-run refinery planet, killing everyone aboard except Lieutenant Ellen Ripley (Sigourney Weaver). Unknown to Ripley, an Alien organism was also aboard the escape pod, which then begins a killing spree in the prison.

The film had a difficult production, with various screenwriters and directors getting involved in the project, and shooting began without a finished script. The film was the big-budget debut of a young David Fincher, who was brought into the project after a proposed version with Vincent Ward at the helm was cancelled well into pre-production. Fincher had little time to prepare, and the experience of making the film proved agonizing for him. Besides the need to shoot and rewrite the script simultaneously while fitting in sets that had already been built, filming was also plagued by incessant creative interference from studio executives, who overruled many of Fincher's decisions and dictated a large part of production. Another complication arose when Jordan Cronenweth had to be replaced by Alex Thomson as he was suffering from Parkinson's disease more acutely than he had ever experienced since his diagnosis in 1978. Adding to Fincher's burdens was the pressure to create a film worthy of the previous two and their revered directors. Upon completion, the studio dismantled and reworked the film without Fincher's consent, including a teaser trailer that suggested the film would take place on Earth. Fincher has since disowned the film, citing the aforementioned reasons. A heavily-revised version of the film, known as the Assembly Cut, was released in 2003, which Fincher was not involved with.

The film was released to mixed reviews. While under-performing at the United States box office, it earned over $100 million outside of North America and was considered a financial success. The film was better received outside of the US and the opinion on the film has grown over the years.[citation needed]