Since the X-Men are just a few years away from arriving in the Marvel Cinematic Universe, it's only a matter of time before Marvel's mutants join the Avengers on the big screen. Like their cinematic counterparts, the X-Men and the Avengers occupied different corners of the Marvel Universe for most of their respective existences. Other than a few noteworthy exceptions, these massive Marvel super-teams didn't really share too many members. But over the past decade or so, the invisible wall between the teams crumbled as an unlikely selection of mutants joined the Avengers for the first time. On a similar note, a few high-profile Avengers found themselves going into battle along with the X-Men on a regular basis. While the two teams have worked together and fought each other dozens of times, these avenging X-Men represent the kind of cross-pollination that's helped the Marvel Universe thrive in comics. Given the X-Men's impending role in Marvel's movies, the shared history between these two teams could also offer some hints about the future of the MCU.
Now, CBR is taking a look at some of the X-Men who also joined the Avengers. In this list, we'll be counting down, in no particular order, the heroes who pulled double duty on any Avengers squad and on any X-team. While most of these heroes were X-Men before they were Avengers, we'll also be including Avengers who eventually joined the X-Men. While we'll mainly be sticking to teams from the main Marvel Universe, we'll be mentioning a few noteworthy alternate reality squads of Avengers too.
20 WOLVERINE
Even though Wolverine has crossed paths with just about every hero in the Marvel Universe, he didn't get around to joining the Avengers until 2005. While he was having a dinosaur-filled adventure in the Savage Land, Logan bumped into the newly-formed New Avengers and joined that team in 2005's New Avengers #6, by Brian Michael Bendis and David Finch.
After that fateful meeting, Wolverine ran with the New Avengers and a few other Avengers squads for the next decade. When the X-Men and the Avengers fought in the 2012 crossover Avengers vs. X-Men, he even sided with the Avengers over his fellow mutants. Once he opened the Jean Grey School for Higher Learning, Logan went back to spending most of his time with the X-Men.
19 QUICKSILVER
Quicksilver is more famous as an Avenger than as an X-Man. Shortly after he debuted as a member of Magneto's Brotherhood of Evil Mutants, Pietro Maximoff joined Captain America's Avengers in 1965's Avengers #16, by Stan Lee and Jack Kirby. Along with his sister, the Scarlet Witch, the brash speedster went on to have a semi-regular role on Avengers teams for years.
Since Pietro started out as an X-villain and was usually portrayed as Magneto's mutant son, Quicksilver was always vaguely associated with the X-Men. Still, he wasn't officially an X-Man until he joined the government-sanctioned group X-Factor in 1991. While Aaron Taylor-Johnson's Quicksilver joined the Avengers for a single film, Evan Peters' Quicksilver has been a part of a few Fox X-Men movies.
18 BEAST
For decades, Beast was the strongest link between the worlds of the X-Men and the Avengers. After leaving the X-Men, Beast had a short-lived stint as a solo character, where he turned himself blue and furry. After applying to be an Avenger in 1975's Avengers #137, by Steve Englehart and George Tuska, Beast became a full-fledged Avenger in 1976's Avengers #151, by Englehart, Gerry Conway, Jim Shooter and George Perez.
While Beast might be super-serious these days, he was one of the Avengers' most easy-going, quick-witted members throughout the 1970s and 1980s. During his time in the Avengers, Hank became close friends with the actor/superhero Wonder Man. Even after Beast returned to the X-Men, the super-genius showed up on a few more Avengers squads.
17 STORM
Even though Storm is one of the most esteemed heroes in the Marvel Universe, it took a shockingly long time for her to join the Avengers. Ororo Munroe's first real tenure in the Avengers didn't even happen in the Marvel Universe. From 2006, Storm joined her first Avengers team in Jeff Parker and Manuel Garcia's Marvel Adventures: The Avengers #1, where she was an active member of the team until that series ended.
In the main Marvel Universe, Storm joined the Avengers in 2011's Avengers #19, by Brian Michael Bendis and Daniel Acuna. After a short and relatively uneventful stint as an Avenger that mainly involved fighting Norman Osborn, she left the team and sided with the X-Men in 2012's Avengers vs. X-Men.
16 ROGUE
Like the Scarlet Witch and Quicksilver, Rogue started out as a member of the Brotherhood of Evil Mutants. After she semi-permanently absorbed the powers and personality of the Avengers' Ms. Marvel and fighting the Avengers, Rogue found redemption and distinguished herself as a hero through her years as an X-Man.
After the dust cleared from Avengers vs. X-Men, Captain America formed the Avengers Unity Division to heal the fissure between the teams. In 2013's Uncanny Avengers #4, by Rick Remender and John Cassaday, Rogue joined some of her fellow mutants on this Avengers squad. Rogue went on to become the team's leader and longest-serving member until it broke up in 2018.
15 NAMOR THE SUB-MARINER
Since Bill Everett's creation of Namor the Sub-Mariner marked the start of the Marvel Universe, it's not too surprising that he ended up on the publisher's two biggest teams. The hot-tempered hero joined Earth's Mightiest Heroes in 1985's Avengers #262, by Roger Stern and John Buscema. Namor stayed on the team until he left to reunite the people of Atlantis after the 1989 crossover "Atlantis Attacks."
After he was revealed to be a mutant, Namor joined the Dark X-Men, and later the X-Men, in 2009. The Atlantean ruler was a key member of the team through 2012's Avengers vs. X-Men, where he went mad and destroyed Wakanda with the power of the Phoenix Force. More recently, he's joined Jean Grey's new X-team in X-Men: Red.
14 X-23
Throughout the 2000s, both the X-Men and the Avengers had training teams where younger heroes could hone their skills. Despite her ferocious nature, X-23 was one of the only heroes who spent time on both groups' trainee teams. In 2005, the young Wolverine clone became an official student at the Xavier Institute and joined the New X-Men.
After a particularly brutal stint on X-Force and spending some time on her own, X-23 became an Avengers trainee in 2012's Avengers Academy #23, by Christos Gage and Tom Raney. Laura's Avengers stint took a dark turn when she and several other teen heroes were placed in a Hunger Games-esque competition in Avengers Arena. After returning to the X-Men, she embraced Logan's legacy by becoming the all-new Wolverine.
13 HAVOK
Despite his jaw-dropping mutant powers and lengthy history, Havok always struggled to escape the shadow of his older brother, Cyclops. After he spent years on various X-teams, Alex Summers caught Captain America's eye. When Cap was putting the Avengers Unity Division together, he made Havok the team's leader in 2012's Uncanny Avengers #1, by Rick Remender and John Cassaday.
Havok has a long history of being mind-controlled or trapped in alternate realities, and both of those things happened to him during his Avengers stint. After a time-traveling adventure in an alternate future, Havok was left with the memories of a daughter he never had. After Havok's personality was mystically altered during the 2014 crossover Axis, he quit the Avengers when he wasn't feeling like himself.
12 CABLE
While Havok's nephew, Cable, is famous for turning the New Mutants into X-Force, the time-traveling mutant also had some relatively brief runs in the X-Men and the Avengers. After joining a makeshift X-Men team to fight Apocalypse in 1999, Nathan Summers had a few unremarkable stints on the main X-Men team in the 2000s.
While he was always more at home leading X-Force, looking after Hope or working as a solo operator, Cable joined the Avengers Unity Division in 2016's Uncanny Avengers #3, by Gerry Duggan and Ryan Stegman. After helping Rogue's Avengers defeat a group of world-eating Inhuman plant monsters, he joined the team to fight a telepathic Red Skull and fell into a coma before leaving the group.
11 DEADPOOL
After spending years in the X-Men's general orbit, Deadpool became a probationary member of the X-Men in 2009's Deadpool #16, by Daniel Way and Paco Medina. Unsurprisingly, that didn't last for long, but Wade Wilson became a key member of Wolverine's X-Force team shortly after that.
After a team-up brought Wade, Logan and Captain America together, Deadpool formed an unlikely friendship with Steve Rogers. When Cap was putting a new Unity team together in 2015's Avengers #0, he brought Wade onto Rogue's Avengers team. While Deadpool distinguished himself during Gerry Duggan and Ryan Stegman's Uncanny Avengers run, his trust in Captain America led him down a dark path in the 2013 crossover Secret Empire, where an evil Cap took over America.
10 CAPTAIN BRITAIN
While he's never been as famous as his American equivalent, Captain Britain had a steady role in the X-Men's world throughout the 1980s and 1990s. Unlike his mutant sister Psylocke, Brian Braddock got his mystical powers from Merlyn in 1976's Captain Britain #1, by Chris Claremont and Herb Trimpe. After his solo adventures took him across the multiverse, Brian joined the British X-Men team Excalibur when it formed in 1983.
In 2010's Age of Heroes #1, Captain Britain joined the Avengers as a reserve member in a story by Paul Cornell and Leonard Kirk. Brian took on a more active role in a covert Secret Avengers team, which he stayed on through 2012's Avengers vs. X-Men until the group disbanded.
9 FIRESTAR
Firestar was originally created to give Spider-Man and Iceman someone to hang out with on Spider-Man and His Amazing Friends. That classic 1980s cartoon introduced Angelica Jones as a former member of the X-Men, but she had a much looser relationship with the team when she was brought into the Marvel Universe. After forming New Warriors with other young heroes in the 1990s, the fiery mutant graduated to Earth's Mightiest Heroes in 1998's Avengers #4, by Kurt Busiek and George Perez.
After a considerable stint with the Avengers during some memorable adventures, Firestar briefly retired from being a superhero and floated between teams. In 2014's Amazing X-Men #1, by Jason Aaron and Ed McGuinness, she joined the X-Men and became the Xavier Institute's physics teacher.
8 SUNFIRE
While Sunfire doesn't have the lengthiest X-Men history, he's still one of Japan's primary heroes in the Marvel Universe. After being created by Roy Thomas and Don Heck in 1970's X-Men #64, Shiro Yoshida joined the second generation of X-Men alongside Storm and Wolverine. After helping save the original X-Men, the brash mutant left the team to protect Japan. He still stayed on decent terms with the X-Men and went on to help form the Big Hero Six.
In 2013's Uncanny Avengers #5, by Rick Remender and John Cassaday, Logan convinced Shiro to join the Avengers Unity Division. Despite his relatively brief time as an Avenger, he saved Rio de Janeiro from space debris, fought Kang the Conqueror and absorbed the energy from a Celestial.
7 SUNSPOT
When Sunspot was created by Chris Claremont and Bob McLeod alongside the other New Mutants, he didn't exactly seem like Avengers material. After growing up on that young X-Men team, the hyper-confident solar-powered millionaire grew slightly more mature during his time with X-Force.
When Captain America was gathering new Avengers in 2012's Avengers #1, by Jonathan Hickman and Jerome Opena, he recruited Sunspot for the team. In an astonishing move, Roberto da Costa used his fortune to buy A.I.M., a hi-tech group that fought the Avengers for years. When the Avengers team splintered, Sunspot used A.I.M. as the basis to form his own Avengers team. Taking the name Citizen V, Roberto remained that team's leader as it morphed into the New Avengers and the U.S.Avengers.
6 CANNONBALL
Like his best friend Sunspot, Cannonball was one of the original New Mutants. After serving as one of that team's leaders, the good-natured Sam Guthrie led X-Force and blasted his way onto a few main X-Men teams. Along with Sunspot, Sam joined Earth's Mightiest Heroes in 2012's Avengers #1.
During his time on the Avengers, Cannonball usually didn't stray too far from his buddy Sunspot. Still, he met and fell in love with his teammate, Smasher. While both left the team to care for their newborn child, Joshua. Sunspot convinced Sam to rejoin his Avengers when the universe was at stake. Later on, Sam split his time between the U.S.Avengers and the alien world where his family lived.
5 DAZZLER
When Dazzler burst onto the scene in 1980's X-Men #130, she was a roller-skating disco singer who moonlighted as a superhero. After a lengthy career as a solo hero, Alison Blaire joined the X-Men in the late 1980s for a few memorable years.
By 2016, Dazzler had given birth to a child who grew up to become the mutant Shatterstar, received a punk rock makeover and even worked as a S.H.I.E.L.D. agent for a little while. In Kelly Thompson, G. Willow Wilson and Jorge Molina's A-Force #2, she joined an affiliate Avengers team made up exclusively of female heroes. During her time with the short-lived group, Dazzler perished and was resurrected several times before meeting an alternate reality version of herself who was also Thor.
4 SABRETOOTH
Sabretooth might be one of the most savage villains in the Marvel Universe, but he still ended up on two Avengers squads. Before he even met his nemesis Wolverine, Victor Creed was part of a covert Avengers team that Nick Fury assembled in the late 1950s. Despite his subsequent descent into villainy, Creed also had a few brief stints on a few X-teams over the years.
During the 2014 crossover Axis, Sabretooth's personality was mystically inverted, which transformed him into a more noble, Wolverine-esque hero. In 2015's Uncanny Avengers #1, by Rick Remender and Daniel Acuna, Creed joined the Avengers Unity Division for a single adventure. After leaving the team, Creed found more comfortable roles in Magneto's X-Men and a new Weapon X team.
3 PRODIGY
David Alleyne was part of a new generation of Xavier Institute students who formed the New X-Men in the mid-2000s. After debuting in 2003's New Mutants #4, by Nunzio DeFilippis, Christina Weir and Keron Grant, David took the name Prodigy and used his mutant ability to absorb knowledge as one of the team's co-leaders. Although he later lost those powers, his fellow X-Men telepathically gave him access to the immense amount of knowledge he had previously copied.
In 2013's Young Avengers #7, by Kieron Gillen, Jamie McKelvie and Mike Norton, Prodigy joined the Young Avengers to help the team locate their mutual friend Speed. Even though he didn’t really have powers anymore, he stayed with the team until it disbanded a year later.
2 QUENTIN QUIRE
Before he became the newest mutant Avenger, Quentin Quire was the X-Men's resident teenage troublemaker. After being created by Grant Morrison and Keron Grant in 2003's New X-Men #134, the powerful teenage telepath caused a riot at Xavier's and took the name Kid Omega. Eventually, Quire mellowed out just enough to become one of the X-Men's most powerful young members.
After a brief stint as an alien god, Quire joined a young Avengers team in Kelly Thompson and Stefano Caselli's West Coast Avengers #1. In the ongoing story, Quire sought out the just-reformed West Coast Avengers to fulfill his contractual obligations for his reality show. While Quire wasn't exactly welcomed by the WCA, the group embraced the much-needed funding that came with him.
1 SPIDER-MAN
Even though he wasn't really a team player for years, Spider-Man eventually became a card-carrying member of the X-Men and several Avengers teams. After a few false starts, the web-slinger joined the Avengers as a reserve member in 1991. Still, Spider-Man's didn't become a full-time Avenger until he co-founded the New Avengers in 2005.
After his friend Wolverine perished, Spider-Man joined the X-Men at his request in 2015's aptly-titled Spider-Man and the X-Men #1, by Elliott Kalan and Marco Failla. Although he's not a mutant, Spider-Man instructed the Jean Grey School's "Special Class," a group of students who could potentially become villains. After teaching them about power and responsibility, Spidey returned to his familiar roles as an occasional Avenger and solo hero.