The X-Men have long been one of Marvel's biggest teams. While they were marginalized for much of the '00s and '10s, they've come roaring back in recent years, thanks to Jonathan Hickman's Dawn Of X and, most importantly, Disney's acquisition of 20th Century Fox. However, the team has always had a lot of really great stories and some of the best were the X-Men's crossovers.

RELATED: X-Men: 10 Story Arcs Every Fan Should Read

The X-Men have been in a lot of crossovers, either with other mutant-centric books or with the rest of the Marvel Universe. It helps that they have some of the best villains around, which make for fruitful fodder for all manner of stories with all kinds of heroes.

10 House Of M

X-Men

House Of M was billed as the first crossover between the Astonishing X-Men and the New Avengers and it certainly lived up to that. Bringing the two teams together to figure out what to do about Scarlet Witch, things quickly spiraled out of control as everyone woke up in an entirely new reality, one where mutants were dominant, with Wolverine and a young mutant named Layla Miller having to gather the heroes to figure out what exactly was going on and how to fix it.

House Of M probably gets more credit than it deserves for how good it actually is but it did have a lot of big repercussions for the X-Men and definitely deserves a read, even if it is often really boring.

9 The Twelve

the twelve in X-Men comics

The Twelve put a bow on the '90s era of the X-Men, tying up a lot of loose plotlines that had developed over the decade. Crossing through every major X-Men book of the time, it saw Apocalypse finally make his move, gathering twelve mutants that would give him the power to finally take over the world. The X-Men are forced to marshal all of their forces, and even some surprising allies, to stop him.

This story is very continuity heavy and can be a bit confusing for people who aren't familiar with the '90s X-Men, but it's still a great X-Men story. It's not as well-remembered as it deserves to be but it's one of the best '90s X-Men stories.

8 Onslaught

The Avengers, X-Men, and Fantastic Four versus Onslaught

Onslaught gets a lot of flack because it's sort of peak '90s cheese but it's actually a lot better than it gets credit for. Onslaught, a mixture of Professor X and Magneto, emerges from the shadows, attacking New York City, and it's up to the greatest heroes of the Marvel Universe- the X-Men, Avengers, and Fantastic Four- to stop him.

RELATED: 10 Times Wolverine Let Down The X-Men

In the '90s, event comics were very different than they are today and Onslaught is very much indicative of that. Instead of telling the story in one main series, it crossed into multiple books, with the issues marked "Phase" more important than the ones marked "Impact". Also unlike today's events, it had wide-reaching repercussions that played out for years afterward.

7 Inferno

HAVOK - Inferno

In the '80s, multi-book crossovers were in their infancy. Books like Secret Wars and Secret Wars II pioneered the concept at Marvel and the X-Men, being one of the few Marvel concepts with multiple books and the sales pedigree to match, got in on the act. Inferno wasn't the first big X-Men crossover of the '80s, but it's the best of that era.

In it, many of Mister Sinister's chickens come home to roost as he and his Marauders try to get their hands on Madelyne Pryor and her and Cyclops's baby and open a whole can of worms. Pryor snapped, became the Goblin Queen, and the X-Men had to stop demons from taking over the world.

6 Second Coming

Hope Summers and the X-Men preparing for battle in Second Coming

The post House Of M era X-Men was pretty devoid of bright spots, literally and figuratively, as the mutant race was constantly on the verge of extinction and the stories could be kind of dark. While Second Coming was still pretty dark, it saw Hope return to the X-Men. Well, Hope Summers, at least.

The first mutant child born after the Decimation, Cable had taken Hope to the future to be raised and her return saw anti-mutant forces led by Bastion come out of the woodwork to destroy her and the future of the mutant race. Action-packed and full of suspense, this is one of the best X-Men stories of its era.

5 X-Men/Dark Avengers: Utopia

Dark X Men lineup

Unlike the rest of the Marvel Universe, the X-Men were spared a lot of the worst of Norman Osborn's Dark Reign for a while. However, he eventually turned his eyes to the diminished mutant race and brought not only his Dark Avengers with him but a mutant team of his own, the Dark X-Men, to try and force his rules on mutants.

The X-Men were having none of it and what followed was a tense stand-off as the X-Men worked to outmaneuver Osborn, discover just what he was up to and why, and beat him. Full of twists and turns, this story was the beginning of the Utopia era and probably the best X-Men story pre-Schism.

4 The Age Of Apocalypse

Wolverine leads the new X-Men in Age of Apocalypse

The Age Of Apocalypse was a huge risk but one that paid off very well. An alternate reality created by the death of Professor X before he formed the X-Men, it saw a world where Apocalypse took over America and the only ones standing against him were Magneto and his X-Men. All of the familiar trappings of the Marvel Universe were gone and readers were dropped into something entirely new.

RELATED: 10 Times The Marvel Universe Turned Against The X-Men

AoA is probably the most beloved crossover event of the '90s. Crossing through every X-Men book, two bookend issues, and one limited series, it took the dystopian alternate reality concept to its logical conclusion, really getting into the nitty-gritty of the whole thing. Marvel would try and recapture AoA's lightning in a bottle several more times but could never reach its heights again.

3 Operation: Zero Tolerance

X-Men's Iceman and Bastion in Marvel Comics

Operation: Zero Tolerance is a highly underrated mid-'90s X-Men crossover that saw the end of the Nicieza-Lobdell era of the books. With the world more anti-mutant than ever after Onslaught, a mysterious man named Bastion mobilizes Operation: Zero Tolerance against the X-Men, unleashing the Prime Sentinels, human sleeper agents injected with nanites that turn them into Sentinels.

Crossing through the main X-Men books, this action-packed story saw the X-Men with their backs against the wall, cut off from their resources and the riches of Charles Xavier, and forced to fight for their lives against a government agency that had years of preparation time on them.

2 Avengers Vs X-Men

X-Men vs Avengers

Avengers Vs X-Men brought an end to the Utopia era of the X-Men in a grand fashion. With the Phoenix Force coming to the Earth, Cyclops hatched a plan to use it to reignite the mutant race. Wolverine warned the Avengers and the two teams came to blows, escalating things more and more until the Phoenix arrived and took over not one but five hosts.

AvX was an action-packed romp that saw Marvel's two biggest teams fight it out for the future of the Marvel Universe. It ended the status quo wrought by House Of M and looked to usher in a new era for the X-Men. While Marvel would pretty much immediately ruin everything again, this is still a really good story.

1 Fatal Attractions

The X-Men attack Magneto in Marvel Comics

The X-Men fighting Magneto is always a lot of fun and that's Fatal Attractions in a nutshell. Magneto returned with a new group of Acolytes and offered the mutants of the world a choice- join him on his new space station Avalon or face the consequences when he unleashed his might on humankind. With battle lines drawn and a high profile defection, the X-Men prepared to end his threat once and for all.

This one had it all: big action, heart-pounding drama and intrigue, and a final battle that changed the X-Men's lives for years to come. Fatal Attractions would have wide-ranging repercussions on the X-Men and the Marvel Universe of the '90s, differentiating it from just about any crossover before or since.

NEXT: 10 X-Men Who Work Better Solo