The first official trailer for "Avengers: Doomsday" has finally arrived, offering another thrilling glimpse of the Fox-era X-Men entering the MCU. With Professor X, Magneto, Cyclops, Mystique, Nightcrawler and more returning, the crossover may feel a little daunting for younger viewers less familiar with the mutants’ long and complicated cinematic history. Before they collide with the Avengers when "Doomsday" arrives on December 18, here are five essential X-Men films to bring you up to speed

X-Men (2000)

The best place to begin is the film that introduced the X-Men to a generation of cinemagoers. After Wolverine and Rogue are rescued and taken to Professor Charles Xavier’s school, they are drawn into a battle against Magneto’s Brotherhood, which plans to use Rogue’s powers to transform world leaders into mutants. Along the way, the film establishes Xavier and Magneto’s opposing visions for mutantkind while introducing Cyclops and Mystique. All four characters are set to return in Avengers: Doomsday.

X2: X-Men United (2003)

Widely considered one of the franchise’s best entries, X2: X-Men United raises the stakes when Colonel William Stryker raids Xavier’s school and abducts Professor X. The remaining X-Men must then form an uneasy alliance with Magneto to stop Stryker from using Cerebro to wipe out mutants worldwide. The film also gives Alan Cumming’s Nightcrawler an unforgettable introduction with its White House opening. With Cumming returning as the teleporting mutant in Avengers: Doomsday, this is essential viewing for newcomers.

X-Men: The Last Stand (2006)

It may be one of the franchise’s more divisive chapters, but X-Men: The Last Stand is still worth revisiting before Doomsday. The discovery of a permanent mutant “cure” divides the community, just as Jean Grey returns as the dangerously powerful Phoenix and joins Magneto’s war against humanity. The film also introduces Kelsey Grammer’s Beast, a brilliant scientist and political representative who joins the climactic battle at Alcatraz. With Grammer returning in Doomsday, this remains his most substantial Fox-era appearance.

X-Men: Days of Future Past (2014)

Trying to untangle the X-Men franchise’s complicated timeline? Days of Future Past is essential. In a dystopian future where Sentinels are hunting mutants to extinction, Wolverine travels back to 1973 to stop Mystique from assassinating their creator, Bolivar Trask. To pull it off, he must reunite the younger Xavier and Magneto, whose fractured friendship could decide mutantkind’s fate. By bringing two generations of X-Men together and rewriting the franchise’s history, the film feels like ideal preparation for the multiversal chaos of Avengers: Doomsday.

Deadpool & Wolverine (2024)

Though not a traditional X-Men team film, Deadpool & Wolverine offers the clearest bridge between Fox’s mutant universe and the MCU. After discovering that his timeline is collapsing following Wolverine’s death, Deadpool recruits a troubled Logan variant before the pair become trapped in the Void and face Cassandra Nova. The film also finally gives Channing Tatum his long-awaited debut as Gambit. With Tatum returning in Avengers: Doomsday, it shows how familiar characters from earlier Marvel franchises can find new life inside the MCU.

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