The Brotherhood of Evil Mutants, or the Brotherhood of Mutants, is a team of comic book mutant supervillains in Marvel Comics' universe who are devoted to mutant superiority over normal humans. Their roster has varied and has included many powerful and dangerous mutants, and they have often been at odds with the X-Men, although on rare occasions they have worked alongside them, usually in order to overcome some greater evil. The original Brotherhood first appeared in Uncanny X-Men #4, and were created by Stan Lee and Jack Kirby.

The original leader of the team was Magneto, a mutant with the ability to control magnetic fields. It would be later revealed that Magneto was a Holocaust survivor, explaining his distrust with humanity and its inability to accept those who are different. The other members of the original team were Quicksilver, who can run at incredible speeds, the Scarlet Witch, who has the power to affect probability fields, the Toad, a sinvelling villain with incredible jumping ability and a Medieval costume, and Mastermind, with the power to create illusions of sight, smell, taste, touch and sound. Quicksilver and the Scarlet Witch are twins, and also Magneto's children, although at the time of the original Brotherhood all three of them were unaware of it. Time and again, the Brotherhood clashed with the original X-Men team (consisting of Cyclops, the Angel, the Beast, Iceman and Marvel Girl), until Magneto was captured by an extraterrestrial being called the Stranger. Quicksilver and the Scarlet Witch left the team and joined the Avengers, and the other members dispersed. Later, back on Earth, Magneto reorganized the team three times, including such mutants as the Blob and Unus the Untouchable, and creating a team that was later alternately called Mutant Force and the Resistants.

The shapeshifting mutant terrorist Mystique later organized her own Brotherhood of Evil Mutants. Members included Pyro, the Blob, Avalanche, Destiny and even Rogue. This team (minus Rogue, who defected to the X-Men) later became the core membership of the government-sponsored team called Freedom Force. As Freedom Force, their membership briefly included Spiral and the second Spider-Woman, and later included Super Sabre, the Crimson Commando, and Stonewall. This group both fought and teamed up with several heroic groups, including the Avengers, but ultimately disbanded after Destiny, Super Sabre and Stonewall were killed in action and the Crimson Commando was crippled.

The Toad also organized a Brotherhood of Evil Mutants of his own at one point, including the Blob and Pyro, a woman named Phantazia who could disrupt machines and superhuman powers, and the vampiric humanoid pterodacytl called Sauron. Later, the Mimic and Post were added to the roster, replacing Phantazia and Sauron. Havok, while suffering from the effects of a nervous breakdown, was the leader of a short-lived Brotherhood of Mutants whose membership included himself, the Dark Beast, Fatale, and, briefly, Aurora and X-Man. Mystique later organized another Brotherhood, drawing members from nearly every incarnation, and adding a new female Mastermind and Sabretooth to the lineup.

During this time period, it was revealed that the teleporter named Astra had been a member of the original Brotherhood, but had quit before the team fought the X-Men.

Later, a short-lived Marvel series called The Brotherhood featured a group of mutant terrorists, unrelated to any other version of the Brotherhood. This series was cancelled after nine issues, at which point the feature characters killed one another or were killed by the publicity-driven X-Force (later renamed X-Statix).

More recently, in the "Heroes and Villains" arc that concluded Chuck Austen's run on X-Men, a new version of the Brotherhood appeared. The team was led by Exdous, and its other members included Avalanche, Sabretooth (who had simply been hired by Exodus), and new members Black Tom Cassidy, Mammamax, Nocturne (who was revealed to be a spying on the team), and Juggernaut (who was later revealed to be a mole). After Black Tom killed Juggernaut's friend Sammy Pare, the "Squid-Boy", Juggernaut tried to destroy the Brotherhood. After knocking Juggernaut and several other Brotherhood members unconscious, Exdous lead his team to the Xavier Institute to claim revenge for the apparent death of Magneto. The entire team was defeated by the second Xorn, who sucked them into the "black hole" within his head; Nocturne was sucked in as well, and Juggernaut followed her. The ultimate fate of this Brotherhood is unknown.

In Ultimate X-Men, the Brotherhood of Evil Mutants is called the Brotherhood of Mutant Supremacy. In the X-Men: Evolution animated series and the X-Men movie, the group is simply called the Brotherhood of Mutants. In the movie, the membership of the Brotherhood of Mutants includes Magneto, Mystique, Toad, and Sabretooth. Sabretooth had not previously been depicted as a member of the Brotherhood, and only joined in the comics after the movie was released.

The Brotherhood is not always so necessarily evil as they are opposed to Professor Charles Xavier's dream of peace with humans. Their use of the name "Evil" is alternately explained away as irony or as an attempt to force Xavier into an awkward moral position. Many of them have been attacked or otherwise harmed, cast out or hated by humans, which makes them resentful and misguided. At times, many of the Brotherhood mutants have shown signs of reluctance towards harming humans, to the point of Quicksilver and the Scarlet Witch joining the Avengers. Even Magneto is not entirely evil; he was briefly the headmaster of the Xavier Institute, and in an alternate timeline, he was the leader of the X-Men, having pledged himself to realizing the dream of his murdered friend, Charles Xavier.