There is still no sign of the X-Men in the MCU, but there are several possible explanations as to why they'll be appearing so late. Marvel Studios earned the film rights to mutants and the X-Men after Disney's acquisition of Fox in 2019, though the integration of mutants into the MCU has been incredibly slow. Previously, 20th Century Fox had developed a live-action franchise based on mutant characters from Marvel Comics, starting with 2000's X-Men and culminating in 2020's The New Mutants, but now that the characters are with Marvel Studios, viewers have been waiting patiently for the X-Men to finally make themselves known in the MCU.
With the start of Phase 4 and the Multiverse Saga, Marvel Studios began introducing mutants into the MCU, starting with the surprising reveal that Kamala Khan, a.k.a. Ms. Marvel, is a mutant. This was followed by the appearance of a Professor X variant in Doctor Strange in the Multiverse of Madness, Namor in Black Panther: Wakanda Forever, and several teases of mutants in She-Hulk: Attorney at Law. While Phase 5 is set to debut even more mutants, there is still no clear sign of the formation of the MCU's X-Men, so there will need to be a solid in-universe explanation for exactly why they've waited so long to appear.
10 The X-Men Could Have Been Hiding From Persecution
One of the key elements of mutant storylines in Marvel Comics is the persecution that they face from average humans. Humans' fears of mutants allow complex villains such as Magneto, Apocalypse, and Mystique to rise to power, so it will be difficult to tell a mutant-centric story in the MCU without exploring this hatred. It's known that mutants have existed in the MCU for centuries - proven by Namor - so it's possible that the world's mutant population went into hiding, perhaps seeking refuge from discrimination. This means that mutant-kind could have been residing in the background of the MCU, allowing them to make their return in future projects.
9 MCU's X-Men Could Come From Another Reality In The Multiverse
The fact that mutants have started to be introduced during the MCU's Multiverse Saga perhaps suggests that mutants and the X-Men could make their way to the MCU from another reality. At least two other X-Men teams are known to exist in the multiverse: Fox's team from the X-Men franchise, and Earth-838's team, which was led by Professor X in Multiverse of Madness. Either one of these teams - or a completely different one - could make their way to the MCU's main continuity, potentially even setting themselves up as the official X-Men team for Marvel Studios' franchise. However, this could lead to an incursion, which may have catastrophic consequences.
8 Avengers: Secret Wars Could Establish A New MCU Timeline For Mutants
The MCU's Multiverse Saga is set to conclude with Avengers: Secret Wars, assumed to be based on Marvel Comics' 1984 and 2015 Secret Wars events. The latter featured the destruction of the multiverse after a massive incursion and the instigation of a new timeline after time on Doctor Doom's Battleworld. Should this event occur in 2027's Avengers: Secret Wars, mutants and the X-Men could simply pop up in the MCU's subsequent projects, being revealed to have already been residing in the new timeline, which would allow for minimal explanation in integrating them into the franchise, while also showing the transformative consequences of Secret Wars.
7 Deadpool Could Break The Fourth Wall And Rewrite MCU Continuity
Deadpool is one of the most highly-anticipated additions to the MCU, set to make the move from Fox's X-Men franchise in 2024's Deadpool 3. Not only will Ryan Reynolds be reprising his role, but Hugh Jackman and a variety of other Deadpool cast will be ing him for the MCU's newest multiversal adventure. It's possible that this project could see the debut of the MCU's X-Men team, particularly since Deadpool's ability to break the fourth wall could see him literally rewrite the MCU to include mutants and the X-Men. Jennifer Walters did something similar in She-Hulk: Attorney at Law, so this isn't outside the realm of possibility.
6 Mister Sinister Could Have Tampered With The World's Mutant Population
One theory suggests that Mister Sinister, a.k.a. Nathaniel Essex, one of the X-Men's most iconic villains, could have already tampered with the world's mutant population. In Marvel Comics, Essex is a genius-level scientist in the field of genetic manipulation, and his obsession with mutants often brings him to odds with the X-Men. It's possible that, prior to the events of 2008's Iron Man, Essex experimented on the mutant X-Gene, dulling the growth of mutantkind globally. This means that the slow introduction of mutants in the MCU's Phase 4 actually makes sense, as they'll only just be starting to emerge if the effects of Mister Sinister's experiments have started to wear off.
5 X-Men '97 Could Lead To The Introduction Of The MCU's Mutants
Produced by Marvel Studios Animation, X-Men '97 will be a continuation of X-Men: The Animated Series, which ran on Fox Kids Network between 1992 and 1997. The series is set outside the MCU's main continuity but will take place within the multiverse, suggesting there could be links made to the live-action franchise. This might be the best way to introduce mutants into the MCU, as X-Men '97's storylines could bleed into the live-action X-Men adaptations in the MCU. The theme of X-Men: The Animated Series played when Kamala Khan was revealed to be a mutant and again during Multiverse of Madness' Professor X introduction, so subtle connections have already been established.
4 Mutants May Have Been Created By MCU's Infinity Stones
One of the most popular theories surrounding the emergence of mutants in the MCU relates to the events of Avengers: Infinity War and Endgame. In these films, the Infinity Stones were collectively used four times: Thanos' snap in Infinity War, Thanos' destruction of the stones in Endgame, Smart Hulk bringing everyone back, and Iron Man defeating Thanos. Each time, a huge amount of cosmic energy was released, which surely made an impact. This could have mutated the genetics of billions of individuals, allowing mutants to begin to show their abilities in the MCU's Phase 4 - though this means the formation of the X-Men could still be a long way off.
3 Marvel Comics' House Of M Storyline May Have Already Happened
Marvel Comics' House of M storyline took place over eight issues in 2005 and saw the Marvel Universe change drastically as the Scarlet Witch and Professor X manipulated history into a twisted reality where mutants were the dominant species. In the story's climactic moments, the Scarlet Witch realizes the damage she'd caused and utters the words, "No more mutants," reducing the world's mutant population from millions to hundreds. Subsequent comic stories deal with the aftermath of this event, and one theory suggests that the MCU has also been taking place in a world following the decimation of the world's mutants, leaving only a handful surviving in the background of the MCU.
2 The Scarlet Witch Could Bring More Mutants & The X-Men Into The MCU
While the theory surrounding House of M is an attractive one, some also argue for the opposite to happen at some point in the MCU's future. Elizabeth Olsen's Wanda Maximoff, a.k.a. the Scarlet Witch, has had a tumultuous journey in the MCU, culminating in her apparent death in Multiverse of Madness, though she'll likely return in MCU projects. Should she become aware of mutants, she could utter the opposite of "no more mutants," increasing the world's mutant population by millions. This would allow many mutant characters to quickly enter the MCU with a bang and potentially lead to the quick formation of the X-Men to deal with the consequences.
1 The X-Men Could Form To Replace The MCU's Avengers
Since mutants are being introduced to the MCU's Multiverse Saga very slowly, it's likely they won't get much attention until the start of the MCU's Phase 7. This is especially true as Phase 6 is set to conclude with two epic crossover films: Avengers: The Kang Dynasty and Avengers: Secret Wars. It's possible that Marvel Studios could bring the story of the franchise's Avengers to a close in Secret Wars, potentially even killing off several high-profile heroes, which would leave a huge vacancy in Earth's superhero roster. This would provide the perfect opportunity for the X-Men to finally make themselves known, filling the gap left by the Avengers.
