Dark Phoenix (titled onscreen, marketed internationally and released on home media as X-Men: Dark Phoenix) is a 2019 American superhero film based on the Marvel Comics X-Men characters. It is a sequel to 2016's X-Men: Apocalypse, the twelfth installment overall in the X-Men film series, and the fourth and final installment of the prequel films. It marks the first X-Men film without the involvement of Hugh Jackman as Wolverine (apart from the spin-off Deadpool films), and the last to be produced by Bad Hat Harry Productions, though the company was uncredited due to sexual assault allegations made against Bryan Singer in 2019. It was produced, written, and directed by Simon Kinberg (in his feature film directorial debut) and stars an ensemble cast featuring James McAvoy, Michael Fassbender, Jennifer Lawrence, Nicholas Hoult, Sophie Turner, Tye Sheridan, Alexandra Shipp, and Jessica Chastain.

Dark Phoenix tells the origin story about how Jean Grey becomes the Phoenix. The story revolves around Jean struggling with mental illness after a cosmic force enhances her psychic powers, which unlocks trauma from her childhood that causes both her mind and her powers to become unstable. It follows Jean as she tries to avoid hurting the people she loves, while other parties seek to control or kill her.

After X-Men: Days of Future Past (2014) erased the events of X-Men: The Last Stand (2006) from the series' timeline, Kinberg expressed interest in a new adaptation of Chris Claremont and John Byrne's "The Dark Phoenix Saga" in a future film that would be more faithful than his previous attempt with The Last Stand, which was met with a mixed reception, with even Kinberg and co-writer Zak Penn ultimately unimpressed with the film. The new adaptation was confirmed as a follow-up to Apocalypse in 2016. Kinberg signed on as director in June 2017, with the majority of the cast set to return from Apocalypse. Filming began later that month in Montreal and was completed in October 2017; the entire third act was reshot in late 2018 after test screenings yielded poor responses. The film is dedicated to the memory of X-Men co-creator Stan Lee, who died on November 12, 2018.

Dark Phoenix was theatrically released in the United States by 20th Century Fox on June 7, 2019. It received mixed reviews and grossed $252.4 million worldwide on a $200 million production budget. Deadline Hollywood estimated the film lost $133 million after marketing and distribution costs, making it one of the biggest box-office bombs of all time.