Avengers: Doomsday is an upcoming American superhero film based on the Marvel Comics superhero team the Avengers. Produced by Marvel Studios and AGBO, and distributed by Walt Disney Studios Motion Pictures, it is intended to be the fifth installment in the Avengers film series following Avengers: Endgame (2019) and the 39th film in the Marvel Cinematic Universe (MCU). Directed by Anthony and Joe Russo and written by Michael Waldron and Stephen McFeely, the film features an ensemble cast including Chris Hemsworth, Vanessa Kirby, Anthony Mackie, Sebastian Stan, Letitia Wright, Paul Rudd, Wyatt Russell, Tenoch Huerta Mejía, Ebon Moss-Bachrach, Simu Liu, Florence Pugh, Kelsey Grammer, Lewis Pullman, Danny Ramirez, Joseph Quinn, David Harbour, Winston Duke, Hannah John-Kamen, Tom Hiddleston, Patrick Stewart, Ian McKellen, Alan Cumming, Rebecca Romijn, James Marsden, Channing Tatum, Pedro Pascal, and Robert Downey Jr. In the film, the Avengers, Wakandans, Fantastic Four, New Avengers, and the X-Men team up to face Doctor Doom (Downey).

Two new Avengers films, The Kang Dynasty and Secret Wars, were announced in July 2022 as the conclusion of the MCU's Phase Six and "The Multiverse Saga". Destin Daniel Cretton was hired to direct The Kang Dynasty and Jonathan Majors was set to reprise his MCU role as the villain Kang the Conqueror. Jeff Loveness joined the film as writer that September. In November 2023, Cretton departed, Waldron replaced Loveness as writer, and Marvel was considering moving away from the Kang storyline, in part due to Majors's legal issues; Majors was fired the following month. The return of the Russo brothers as directors and McFeely as co-writer, the casting of Downey as new villain Doctor Doom, and the new subtitle Doomsday were all announced in July 2024. Filming began in April 2025 at Pinewood Studios in England, with a large cast consisting mainly of actors from previous MCU media and 20th Century Fox's X-Men film series, and wrapped in September. Location filming took place in England and Bahrain.

Avengers: Doomsday is scheduled to be released in the United States on December 18, 2026, as part of Phase Six of the MCU. The film's sequel, Secret Wars, is set to be released on December 17, 2027.

Fourteen months after the events of Thunderbolts* (2025), the Avengers, Wakandans, Fantastic Four, New Avengers, and the "original" X-Men team up to face Doctor Doom.

Additional actors slated to reprise their MCU roles in the film include Jeremy Renner as Clint Barton / Hawkeye,^{[better source needed]} Benedict Cumberbatch as Dr. Stephen Strange, Tom Holland as Peter Parker / Spider-Man, Hayley Atwell as Peggy Carter, Mabel Cadena as Namora, and Alex Livinalli as Attuma. Chris Evans, who previously played Steve Rogers / Captain America and an alternate universe variant of Johnny Storm / Human Torch in the MCU, has been cast in an undisclosed role. There are conflicting reports about whether Ryan Reynolds will reprise his role as Wade Wilson / Deadpool in the film.

After directing the films Avengers: Infinity War (2018) and Avengers: Endgame (2019), Anthony and Joe Russo expressed interest in directing a Secret Wars film based on the 1984–85 comic book crossover event written by Jim Shooter and the 2015–16 comic book storyline written by Jonathan Hickman. Both follow various Marvel characters who converge on the planet Battleworld. Infinity War and Endgame writers Christopher Markus and Stephen McFeely said they would return to write such a film if the Russo brothers were directing it. At San Diego Comic-Con (SDCC) in July 2022, Marvel Studios president Kevin Feige announced the films Avengers: The Kang Dynasty and Avengers: Secret Wars, to be released on May 2, 2025, and November 7, 2025, respectively. They were set to conclude "The Multiverse Saga", which covers Phases Four, Five, and Six of the MCU. The Kang Dynasty was inspired by a 2001–02 comic book storyline written by Kurt Busiek in which Kang the Conqueror travels through time to enslave humanity. Jonathan Majors was cast as Kang for several Phase Four projects, and was confirmed to be starring in both new Avengers films. Destin Daniel Cretton was hired to direct The Kang Dynasty, with Jeff Loveness writing the script, and Michael Waldron set to write Secret Wars.

Following Majors's arrest in March 2023 and subsequent assault allegations, reports and speculation emerged about his future in the MCU. Loveness was no longer involved in the film by the start of the 2023 Writers Guild of America strike in May, reportedly because he was closely associated with the Kang storyline and Marvel was "moving away" from that. In June, the release dates for The Kang Dynasty and Secret Wars were pushed back to May 1, 2026, and May 7, 2027, respectively, in part due to the scripts not being ready before the strike. Cretton stepped down as director of The Kang Dynasty in November 2023, partially due to schedule delays, and Waldron was set to rewrite the film. The next month, Majors was fired by Disney and Marvel Studios after he was found guilty of harassment and reckless assault in the third degree. The studio had started referring to The Kang Dynasty internally as Avengers 5 by then. By February 2024, both Avengers 5 and Secret Wars were being rewritten to minimize Kang's role or remove him entirely following Majors's firing.

Shawn Levy became the studio's top choice to direct Avengers 5 by mid-March 2024, after he directed the MCU film Deadpool & Wolverine (2024), but there were potential scheduling issues with his other projects. By that May, Marvel Studios had approached Robert Downey Jr.—who starred as Tony Stark / Iron Man in "The Infinity Saga", covering the MCU's Phases One, Two, and Three—about returning to the MCU to take on the new character of Victor von Doom / Doctor Doom. Downey said he would only return if the Russo brothers also returned as directors. After McFeely approached the Russos with an idea for the films that excited them, they entered early talks to direct both Avengers 5 and Secret Wars by mid-July. At SDCC at the end of the month, the Russos were confirmed to be directing the two films. They revealed that Avengers 5 was now titled Avengers: Doomsday, and both films would feature Downey as Doctor Doom. The Russos were producing the films through their production company AGBO, and McFeely had joined as writer for both films, working with Waldron. In March 2025, Marvel announced 26 cast members for the film alongside Downey. Many of those actors returned from previous MCU media, while some were reprising their roles from 20th Century Fox's X-Men film series. Downey, Marvel Studios, and Feige teased that there were more cast members to reveal. Feige said Doomsday would focus on the Avengers, Wakandans, Fantastic Four, Thunderbolts—revealed in Thunderbolts* (2025) to be the government-sanctioned New Avengers—and the "original" X-Men teaming up to face Doom.