In a world where mutants (evolved super-powered humans) exist and are discriminated against, two groups form for an inevitable clash: the supremacist Brotherhood, and the pacifist X-Men.
The human government develops a cure for mutations, and Jean Gray becomes a darker uncontrollable persona called the Phoenix who allies with Magneto, causing escalation into an all-out battle for the X-Men.
In the 1960s, superpowered humans Charles Xavier and Erik Lensherr work together to find others like them, but Erik's vengeful pursuit of an ambitious mutant who ruined his life causes a schism to divide them.
The X-Men send Wolverine to the past in a desperate effort to change history and prevent an event that results in doom for both humans and mutants.
In the 1980s the X-Men must defeat an ancient all-powerful mutant, En Sabah Nur, who intends to thrive through bringing destruction to the world.
Jean Grey begins to develop incredible powers that corrupt and turn her into a Dark Phoenix, causing the X-Men to decide if her life is worth more than all of humanity.