Doomsday’ Including Robert Downey Jr.’s Return

Warning: Spoilers ahead for The Fantastic Four: First Steps!

Doctor Doom has officially arrived.

The masked metal maniac made his first appearance in the Marvel Cinematic Universe during a shocking cameo in the mid-credits scene for The Fantastic Four: First Steps. This is only the beginning for the cloaked villain, who will soon star in Avengers: Doomsday.

Originally titled Avengers: The Kang Dynasty, the upcoming fifth Avengers film has undergone numerous changes since it was first announced at San Diego Comic-Con in July 2022.

Following the introduction of He Who Remains on Disney+’s Loki, the Avengers project was initially going to revolve around an alternate-timeline variant of the character Kang the Conqueror, played by Jonathan Majors. However, after Majors was found guilty of assault and harassment in his misdemeanor trial in December 2023, Marvel reworked the script.

Many new details about the film were announced at San Diego Comic-Con in July 2024, including the updated title and the new villain. In a standout moment during the Marvel presentation, it was announced that Robert Downey Jr., who famously played superhero Iron Man, would return to the MCU as Doctor Doom.

From the cast to the release date, here’s everything to know about Avengers: Doomsday.

Who is the villain of Avengers: Doomsday?

While the Infinity Saga revolved around Thanos (Josh Brolin) as the main villain, the Multiverse Saga will debut Doctor Doom as the big bad in Avengers: Doomsday. Fittingly, the role will be played by Downey Jr., who previously starred as Avengers superhero Iron Man and sacrificed himself to save the world in Avengers: Endgame.

The announcement was made during San Diego Comic-Con in July 2024, as Downey Jr. emerged onto the panel’s stage among a group of actors wearing masks and robes.

“New mask, same task,” Downey said as he removed Doctor Doom’s notable silver mask. “What did I tell ya? I like playing complicated characters.”

So, how exactly can Downey Jr. play both Iron Man and Doctor Doom? As previous films in the Multiverse Saga have teased, the MCU is teeing up for a big collision of parallel universes in Avengers 5 and 6.

This has led many fans to believe that Downey Jr. will portray an alternate-universe version of Stark, where he will become the villainous Doctor Doom instead of the heroic Iron Man.

Who is in the Avengers: Doomsday cast?

In addition to Downey as the chief villain, it was confirmed during Comic-Con that both the Fantastic Four and the Thunderbolts would appear in Avengers 5 and 6. 

For the Fantastic Four, that includes Pedro Pascal as Reed Richards/Mr. Fantastic, Vanessa Kirby as Sue Storm/The Invisible Woman, Joseph Quinn as Johnny Storm/The Human Torch and Ebon Moss-Bachrach as Ben Grimm/The Thing. 

From the Thunderbolts, the following actors are expected to appear: Sebastian Stan as Bucky Barnes, Florence Pugh as Yelena Belova, David Harbour as Red Guardian, Wyatt Russell as U.S. Agent, Olga Kurylenko as Taskmaster, Hannah John-Kamen as Ghost, Julia Louis-Dreyfus as Valentina Allegra de Fontaine and Lewis Pullman as Bob.

In March 2025, a livestream hosted by Marvel announced more additions to the cast. Those confirmed to return include Chris Hemsworth, Anthony Mackie, Danny Ramirez, Paul Rudd, Tom Hiddleston, Letitia Wright, Winston Duke and Simu Liu.

During the same livestream, Marvel revealed that several of the X-Men will also appear in Doomsday, including Patrick Stewart, Ian McKellen, Alan Cumming, Rebecca Romijn and Kelsey Grammer.

It’s also possible that fellow Marvel star Chris Evans could also be a part of the movie. In December 2024, multiple outlets, including Deadline reported that Evans will be appearing in Avengers: Doomsday, though what role he would play isn’t clear.

What is Avengers: Doomsday about?

An official plotline for the movie hasn’t been announced yet, though the comics could tease what’s in store.

In 2011, a multi-issue comic titled Ultimate Comics: Doomsday was released. In it, the Fantastic Four team up with various Marvel superheroes to stop a mysterious villain trying to destroy their timeline.

In the comics, they eventually discover that the mysterious villain is a familiar, heroic face who turned bad in the multiverse, perfectly setting things up for Downey Jr.’s return.

Who is directing Avengers: Doomsday?

Anthony and Joe Russo are slated to helm the project after a few previous director switch-ups. The movie will mark their big return to the MCU after previously directing Captain America: The Winter Soldier (2014), Captain America: Civil War (2016), Avengers: Infinity War (2018), and Avengers: Endgame (2019).

Who is writing Avengers: Doomsday? 

Not only are the Russo brothers slated to return to the MCU, but Stephen McFeely, who co-wrote all four of the Russos’ Marvel films, will pen the script, per Variety.

When will Avengers: Doomsday be released?

Avengers: Doomsday is slated to hit theaters on Dec. 18, 2026, as part of the MCU’s Phase 6. 

The film was originally meant to premiere on May 1, 2026, until Disney announced a delay in May 2025, per Variety.

Will there be other Avengers movie? 

Avengers: Doomsday isn’t the only Avengers project in the works. It will be followed by Avengers: Secret Wars, which is slated to release a year later in December 2027. 

Many of the same production team will be involved, including the Russo brothers as directors and Stephen McFeely as the screenwriter. The cast will also include Downey Jr. as Doctor Doom and the stars of The Fantastic Four and Thunderbolts*.