Every Movie You Need to Watch Before Avengers: Doomsday
Multiverses collide, old rivals return, and Iron Man isn't who you think he is anymore. Here's how to prep.
Marvel's next big crossover event, Avengers: Doomsday, hits theaters on December 18, 2026, and it is shaping up to be the most ambitious Avengers film yet. The Russo Brothers are back in the director's chair, Robert Downey Jr. is returning to the MCU, not as Tony Stark, but as Victor von Doom himself, and the movie is set to pull together heroes from at least three separate universes: the mainline Avengers, the Fantastic Four, the New Avengers (formerly the Thunderbolts), and the X-Men.
That is a lot of history to keep track of. If you have not been keeping up with every Disney Plus show and Phase Five release, do not worry. Below is a curated list of the movies that matter most for understanding who is walking into this fight, why the multiverse is unraveling, and how Doctor Doom ended up as the MCU's next great threat.
1. Avengers: Endgame (2019)
Endgame is the emotional and narrative foundation for everything that follows. It closes out the Infinity Saga, kills off Tony Stark, retires Steve Rogers, and scatters the original Avengers roster in different directions. It also popularizes time travel and alternate timelines as a workable concept within the MCU, which becomes hugely important later on.
Connection to Doomsday: Endgame is the reason Robert Downey Jr. playing Doctor Doom feels so seismic. Tony Stark died a hero in this film, so seeing the same actor return as the franchise's next major villain immediately raises questions about variants, alternate realities, and what exactly Doom's relationship is to the Tony Stark we knew. Endgame is also where the door to the multiverse first creaks open, setting the stage for everything that comes after.
2. Doctor Strange in the Multiverse of Madness (2022)
This film is where the MCU truly commits to the multiverse as an ongoing storytelling engine. Doctor Strange, Wanda Maximoff, and an alternate universe version of Professor X (Patrick Stewart, reprising his role from the Fox X-Men films) all appear, along with a full introduction to the Illuminati, a council of powerful heroes from a parallel Earth.
Connection to Doomsday: This movie proves that alternate universe versions of familiar characters can exist side by side and that incursions, or universes colliding into one another, are a real and catastrophic threat. Avengers: Doomsday appears to be built around exactly this kind of incursion, with entire teams from different realities being forced together. The Illuminati scene here is also considered a preview of how the MCU plans to fold in classic X-Men actors and concepts.
3. Loki, Season 2 (2023)
Technically a Disney Plus series rather than a theatrical movie, Loki is close to unavoidable for understanding where the multiverse stands right now. The show introduces the Time Variance Authority, the concept of a Sacred Timeline, and He Who Remains, a variant of Kang the Conqueror who claims to have been holding the multiverse together to prevent a war between infinite versions of himself.
Connection to Doomsday: By the end of the season, Loki takes on the burden of holding the multiverse's timelines together himself, essentially replacing the Kang-centric threat that was originally supposed to headline the fifth Avengers film. When Jonathan Majors was dropped from Marvel following legal issues, the studio pivoted the villain of Avengers 5 from Kang to Doctor Doom, and retitled the film from The Kang Dynasty to Doomsday. Loki's ending is part of why that pivot was even possible, since it left the multiverse in a fragile, unstable state that a new villain like Doom could exploit.
4. Deadpool & Wolverine (2024)
This is the film that officially folds the twenty-year run of Fox's X-Men movies into the MCU's multiverse. Deadpool and a variant of Wolverine travel between timelines, encounter numerous familiar faces from the Fox era, and confront Cassandra Nova, all while dealing with the fallout of the Time Variance Authority's collapse after the events of Loki.
Connection to Doomsday: Deadpool & Wolverine is essentially the MCU's love letter to the old X-Men franchise and its way of confirming that those characters and actors are now fair game within the main timeline. With mutants confirmed to be part of Avengers: Doomsday's ensemble, this film is required viewing for understanding how and why so many familiar X-Men faces can suddenly show up standing next to Iron Man's old teammates.
5. Captain America: Brave New World (2025)
Sam Wilson fully steps into the role of Captain America in this political thriller, which deals with a fracturing world government, a new incarnation of the Leader, and the return of General Thaddeus Ross, now the President of the United States and eventually the Red Hulk.
Connection to Doomsday: This movie sets the geopolitical stage that Doomsday will likely build on, with global tension and a militarized response to superhuman threats already simmering. It also firmly establishes Sam Wilson as the active Captain America heading into the crossover, replacing Steve Rogers as the shield-bearer audiences will be rallying behind.
6. Thunderbolts* (2025)
A team of morally gray former villains, mercenaries, and government assets, including Yelena Belova, Bucky Barnes, Red Guardian, Ghost, and John Walker, are forced together and end up accidentally creating a new super powered being named Sentry. By the end of the film, the team rebrands itself as the New Avengers.
Connection to Doomsday: The New Avengers are one of the confirmed factions converging in Avengers: Doomsday, so this film introduces the roster and group dynamic audiences will see fighting alongside, or possibly clashing with, the classic Avengers. Sentry in particular is expected to be a major wildcard given his immense and unstable power set.
7. The Fantastic Four: First Steps (2025)
Marvel's First Family finally gets a proper MCU introduction in this retro-futuristic film set on an alternate Earth. Reed Richards, Sue Storm, Johnny Storm, and Ben Grimm face down Galactus and his herald, the Silver Surfer, to protect their world and their newborn son.
Connection to Doomsday: This film includes the first on-screen tease of Doctor Doom within the main MCU continuity, hinting at his arrival. The Fantastic Four are confirmed to be one of the core teams in Doomsday, and Reed Richards, being one of Doom's oldest and most personal rivals in Marvel comics history, is likely to play a major role in how the story handles its central villain.
8. Spider-Man: Brand New Day (2026)
Releasing in the summer of 2026, just months before Doomsday, this Spider-Man installment reportedly deals with the fallout of Peter Parker's identity struggles and features Bruce Banner's Hulk in a significant supporting role, according to comments from Mark Ruffalo.
Connection to Doomsday: Because this film lands only a few months before Avengers: Doomsday, it is likely to shape Spider-Man's emotional state and alliances heading into the crossover. It also appears to be where the Hulk's current arc gets addressed, since Ruffalo has indicated Banner will not be appearing in Doomsday itself.
9. X-Men (2000) and X-Men: Days of Future Past (2014)
These are not MCU films, but they are essential context. X-Men from 2000 kicked off the entire modern superhero movie boom and introduced Patrick Stewart's Professor X and Ian McKellen's Magneto. Days of Future Past, meanwhile, is built entirely around time travel and altering a dark future by changing the past, using a young and old cast of X-Men working together across decades.
Connection to Doomsday: Several actors from these films, including Stewart, McKellen, and others, have already appeared as multiverse variants in the MCU, most notably in Doctor Strange in the Multiverse of Madness and Deadpool & Wolverine. Rewatching these classic films helps make sense of who these characters were before they crossed over, and Days of Future Past in particular offers a useful narrative template for a story about altering timelines and averting a catastrophic future, something Doomsday appears poised to explore on a much larger scale.
Honorable Mentions
If you have the time, a few other titles are worth a rewatch for smaller but meaningful connections. Avengers: Infinity War (2018) is useful for remembering what a full scale, ensemble level threat looks like in this franchise. WandaVision helps explain Wanda Maximoff's arc leading into the multiverse era, and Ironheart, once it releases, may tie directly into events building toward Doomsday given Riri Williams' confirmed involvement in the wider Phase Six storyline.
Final Thoughts
Avengers: Doomsday is being billed as the moment where nearly two decades of Marvel storytelling, along with two decades of Fox's separate X-Men universe, finally collide into a single event. Watching even half of the films above will make the December premiere far more rewarding, since so much of what makes this crossover exciting depends on recognizing faces, understanding old rivalries, and knowing exactly how fragile the multiverse has already become.
With a reported cast of more than thirty A-list actors, a runtime of roughly two hours and forty five minutes, and Doctor Doom standing at the center of it all, Avengers: Doomsday has a lot riding on it. Doing your homework now means you will be ready when the credits roll and the countdown to Avengers: Secret Wars officially begins.