"The Fall of the Mutants" was a comic book crossover event by Marvel Comics spanning January to March 1988. It spanned three issues each of The Uncanny X-Men (issues #225–227), X-Factor (issues #24–26), and The New Mutants (issues #59–61); unlike most crossovers however, the various titles' storylines did not intertwine, but were instead linked thematically as each team underwent major ordeals and drastic changes in their status quo.

The 1990 computer game X-Men II: The Fall of the Mutants was based on this storyline.

Marvel Comics used a novel approach in advertising the crossover event. A major element within the stories at the time was the public's growing concern over the "mutant menace" and Senator Robert Kelly's proposed Mutant Registration Act, which foreshadowed the dystopian future shown in "Days of Future Past". Marvel distributed postcard-size mock advertisements supporting the act in comic book stores as well as their various titles cover dated "November 1987". Asking "Do You Know What Your Children Are?", the card further suggested that anyone who knew themselves to be a mutant should fill out the form on the back and mail it in to register themselves with the government.

The Fall of the Mutants consists of three separate non-intersecting storylines: one involving the X-Men, one involving X-Factor, and the other concerning the New Mutants.

The X-Men head to Dallas, Texas in search of their missing and de-powered leader Storm, herself seeking the mutant inventor Forge to restore her powers. Upon arrival, they encounter Freedom Force, a government-sanctioned strike team of reformed villains led by Mystique, who are under orders to arrest the X-Men for refusing to comply with the Mutant Registration Act, and a fight ensues. Freedom Force's mutant precognitive Destiny then has a vision: everyone inside a particular Dallas skyscraper at dawn will be dead. Once it begins snowing — in Texas, in the middle of summer — and as cavemen, dinosaurs, and other strange peoples and creatures begin appearing, the two teams realize that something of immense significance is occurring. Calling a temporary truce, they turn to restoring order to the chaos engulfing the city. Many of the events are broadcast on television by reporter Neal Conan and cameraman Manoli Wetherell, who accompany the X-Men and Freedom Force.

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