In Nazi-occupied Poland, in 1944, young Erik Lehnsherr is separated from his parents upon entrance into the Auschwitz concentration camp. While he attempts to reach them, he causes a set of metal gates to bend toward him. This is the result of a mutant ability to create magnetic fields and control metal manifesting, but he is knocked out by the guards. In the not-too-distant future, U.S. Senator Robert Kelly attempts to pass a "Mutant Registration Act" in Congress, which would force mutants to reveal their identities and abilities. Present are Erik, now going by the name "Magneto", and his telepathic colleague Professor Charles Xavier. Xavier sees Lehnsherr in attendance and is concerned with how he will respond to the Registration Act.
In Meridian, Mississippi, 17-year-old Marie D'Ancanto accidentally puts her boyfriend into a coma after she kisses him, because her mutant ability absorbs the power and life force of others. She runs away from home and adopts the name Rogue. In Alberta, she meets Logan, also known as "Wolverine", a mutant who possesses superhuman healing abilities and metal "claws" that protrude from between his knuckles. They are attacked on the road by Sabretooth, one of Magneto's minions, but two of Xavier's students – Cyclops and Storm – arrive and save them. Wolverine and Rogue are brought to Xavier's mansion and school for mutants in Westchester County, New York.
Xavier tells Logan that Magneto appears to have taken an interest in him and asks him to stay while Xavier's mutants, the X-Men, investigate the matter. Rogue enrolls in the school.
Senator Kelly is abducted by two more of Magneto's minions, Toad and Mystique, and brought to their hideout on the uncharted island of Genosha. Magneto uses Kelly as a test subject for a machine powered by his magnetic abilities that generates a field of radiation, which induces mutations in normal humans. Kelly later escapes by taking advantage of his newfound mutation.
Rogue visits Wolverine during the night while he is having a nightmare. Startled, he accidentally stabs her, but she is able to absorb his healing ability to recover. This is observed by fellow students who arrived to help. She is later convinced by Mystique, who disguises herself as Rogue's crush Bobby Drake, that Xavier is angry with her and she should leave the school. Xavier uses his mutant-locating machine Cerebro to find Rogue at a train station, and the X-Men go to retrieve her. Meanwhile, Mystique enters Cerebro and sabotages it.
Having left ahead of Storm and Cyclops, Wolverine finds Rogue on a train and convinces her to return to the school. Before they can leave, Magneto arrives, knocks out Wolverine and subdues Rogue, revealing it was Rogue who he wants rather than Wolverine. Although Xavier attempts to stop Magneto by mentally controlling Sabretooth, he is forced to release his hold on Sabretooth when Magneto threatens the police who have converged on the train station, allowing Magneto's Brotherhood to escape with Rogue. Kelly arrives at Xavier's school, and Xavier reads his mind to learn about Magneto's machine. Realizing the strain of powering it nearly killed Magneto, the group deduces he intends to transfer his powers to Rogue and use her to power it at the cost of her life. Kelly's body rejects his mutation, and his body dissolves into liquid. Xavier attempts to locate Rogue using Cerebro, but Mystique's sabotage incapacitates him, and he falls into a coma. Fellow telekinetic and telepath Jean Grey fixes Cerebro and uses it, learning that Magneto plans to place his mutation-inducing machine on Liberty Island and use it to "mutate" the world leaders meeting at a summit on nearby Ellis Island. The X-Men scale the Statue of Liberty, battling and overpowering the Brotherhood while Magneto transfers his powers to Rogue and activates the mutating machine. As Wolverine confronts and distracts Magneto, Cyclops blasts him away, allowing Wolverine to destroy the machine. He transfers his powers to Rogue and his healing abilities rejuvenate her, while incapacitating himself.
Professor Xavier and Wolverine recover from their comas. The group also learns that Mystique escaped the island battle and is impersonating Senator Kelly, despite being seriously injured by Wolverine. Xavier gives Wolverine a lead to his past at an abandoned military installation in Canada. Magneto is imprisoned in a complex constructed of plastic and is visited by Xavier, and Magneto warns him that he intends to escape one day and continue the fight, Xavier then tells him that he will always be there.
Hugh Jackman as Logan / Wolverine: A Canadian roughhouser who has lived for fifteen years without any memory of his past, apart from his dog tags and an adamantium-encased skeleton. His powers include enhanced animal-like senses, an accelerated healing factor granting him virtual immortality (which makes his age impossible to determine), and three claws extending past the bridge of each knuckle.
Patrick Stewart as Professor Charles Xavier: The mutant founder of the X-Men and the Xavier School for Gifted Youngsters, who hopes for peaceful coexistence between mutantkind and mankind and is regarded as an authority on genetic mutation. Although restricted to a wheelchair, his mutant powers include vast telepathy, which is amplified by the Cerebro supercomputer that he invented with Magneto's help.
Ian McKellen as Magneto: An Auschwitz survivor who was friends with Xavier until his belief that humans and mutants could never co-exist led to their separation. His powers include the ability to generate powerful magnetic fields and a sophisticated knowledge in matters of genetic manipulation, which he uses to attempt to mutate the world leaders to allow mutant prosperity. Brett Morris plays a young Magneto
Famke Janssen as Jean Grey: The medical doctor of the X-Mansion and Cyclops's fiancée. Her powers include telekinesis and telepathy.
James Marsden as Cyclops: Xavier's second-in-command and an instructor at the institute who serves as the X-Men's field leader. He is engaged to Jean Grey. His powers include a strong, uncontrollable red beam of optic energy produced from his eyes, which is only held in check by sunglasses or a specialized ruby-quartz visor enabling him to control the strength of the beam to fire when in combat.
Halle Berry as Storm: A Maasai woman who teaches calmly and caringly at Xavier's school but has become bitter with other people's hatred for mutants, sometimes making her hate humans in return simply because she is afraid of them. Her powers include the ability to manipulate the weather and create lightning storms.
Anna Paquin as Marie D'Ancanto / Rogue: A seventeen-year-old girl forced to leave her home in Mississippi when she puts her boyfriend into a coma by kissing him. Her mutant powers include absorbing anyone's memories, life force, and – in the case of mutants – powers through physical touch.
Tyler Mane as Sabretooth: A brutal and sadistic henchman of Magneto. His powers include a ferocious, feline-like nature, enhanced animal-like senses, fangs and healing abilities similar to Wolverine's, and claws extending past the tip of each finger.
Ray Park as Toad: A very agile henchman of Magneto. His powers include a prehensile tongue, a slimy substance that he spits onto others, and enhanced agility.
Rebecca Romijn-Stamos as Mystique: Magneto's loyal second-in-command, who seems completely facile with respect to modern technology. Her powers include altering her shape and voice to mimick any human being, which is almost secondary to her role as "the perfect soldier".
Bruce Davison as Senator Kelly: An anti-mutant politician who wishes to ban mutant children from schools using a Mutant Registration Act.
Additionally, Shawn Ashmore appeared in a minor role as Bobby Drake / Iceman, a mutant student at Xavier's School for Gifted Youngsters who takes a liking to Rogue. His powers include generating ice.
David Hayter, Stan Lee, and Tom DeSanto make cameo appearances. George Buza, the voice of Beast in X-Men: The Animated Series, appeared as the truck driver who drops Rogue off at the bar at which Wolverine fights. Other cameo appearances include Sumela Kay as Kitty Pryde, Katrina Florece as Jubilee, Donald MacKinnon as a young Colossus sketching a picture in one scene, and Alexander Burton as Pyro. Shawn Roberts also made a cameo appearance in the opening of the film as Rogue's first boyfriend. Kevin Feige had a cameo as a Weapon X tech, but his scenes did not make the final cut of the film.
based on the Marvel Comics superhero team of the same name