Originally a team comprising the original five X-Men, X-Factor was eventually turned a government task force. Jamie Madrox later took the name to found X-Factor Investigations and ultimately sold it to Serval Industries. Now, X-Factor Investigations was reformed on Krakoa.

The X-Files deals with the paranormal or supernatural cases lead by Fox Mulder. Mulder intents to learn the truth of his missing sister and the government that holds the dark secrets. Later, he was joined by Dana Scully, a skeptic and a medical professional who finds herself facing the unknown.

When Cable reformed the New Mutants, he made them his soldiers. They became a mutant "black ops" team, assigned to kill not just the enemies of the X-Men, but of all mutantkind. Although this team eventually disbanded, the X-Force moniker has persisted in successive iterations of more and more aggressive X-teams.

The first team to be named X-Force.

The Children of the Atom, mutants are individuals in the Marvel Universe who are born with an X-Gene that grants them superhuman abilities. Mutants mark the next step in human evolution, known as Homo Superior.

A team of ex-girlfriends of Vartox (and Cherub).

The X-Men are a superhero team of mutants founded by Professor Charles Xavier. They are dedicated to helping fellow mutants and sworn to protect a world that fears and hates them.

The X-Men 2099 series of mutants from the future Earth-928 who take on Professor Charles Xavier's dream to unite the mutants of the world. They are founded by Desert Ghost who finds and gathers the mutants to become the new incarnation of the X-Men.

An independent team of X-Men, founded by Nature Girl, to avenge crimes against nature. The nation of Krakoa does not approve of their mission or tactics, but the island of Krakoa itself, as well as the animal kingdom, does.

A team of young mutants assembled in Halo City by Cerebra and Morphine Somers of the 2099 incarnation of the X-Men in hope to find a mutant messiah as foretold by Doctor Doom.

The X-Patriots were a group of Genoshan refugees who, in the wake of X-tinction Agenda, didn't feel Genosha was safe.

X-Patrol is a team of heroes in the Amalgam Universe. They were an amalgamation of Marvel's X-Force and DC's Doom Patrol.

A future version of the X-Men that originates on Earth #982 also known as the MC2 universe. Jubilee is the leader and organizer of the team.

Named after Charles Xavier, the Xavier Security Enforcers (XSE) is a mutant police team that formed in the late 21st century. Its members work to bring mutant criminals to justice.

The X-Statix were a group of mutant heroes whose main goal was to achieve fame and fortune.

Mutant militia founded by Darkstar

The X-Terminated are a group of freedom fighters who stand together as humanity's last hope against tyrannical mutants.

Initially the mutant alter-ego of X-Factor, the X-Terminators were really the original X-men who sought to rescue and protect young mutants. The name was dropped after X-Factor was exposed, but later adopted by the young mutants they had saved.

A group of refugees lead by Remy LeBeau (Gambit) in the AoA Universe.

The rebel group in Age of X-Man.

Founded by Storm and the United Nations, the X.S.E. is charged with keeping the peace between humans and mutants.

An interdimensional group of iconic X-Men banded together to save a planet's population from total annihilation. Joined by the Dazzler of Earth-616, they're on a mission to prevent similar disasters throughout the multiverse.

Human prototypes created in S.T.A.R. Labs.

Inhabitants of the planet Xudar located in Space Sector 2813.

Yahweh's Children is not the official name of any team, though it is the union of Michael, Lucifer and Elaine, his true descendants.

Yakiba is the Marvel Universe's fictional version of Japanese military intelligence. At points, Sunfire is a Yakiba agent.

Japanese organized crime syndicates.

The gang from Thing's old neighborhood

Members of the Olympian Titans of Myth

Aka the Okar.

The Yeti are ape-like creatures from Nepalese and Tibetan folklore.

A race of green skinned reptilian aliens that serve The Skrull Empire.

A team composed of humans that received powers from a mutant tattoo artist named Leon Nuñez.

A highly force sensitive species that is extremely rare in the galaxy

Demons in japanese mythology.

A ruler of mankind on the alien world of Starfire.

The World War II hero team that appeared in Young All Star comics. Not in any way associated with the Marvel team of the same name.

Golden Age sidekick team re-imagined for the "Heroic Age" of Marvel beginning in 2010.

A younger team affiliated with the All-Star Squadron.

A group of teenage superheroes with powers and abilities mirroring those of the Avengers, Young Avengers was formed by Iron Lad to defeat his future self, Kang. After the team disbanded, Kate Bishop later reformed the team with new costumes. A new team has now been formed by Loki.

Street gang who steal and kill to afford clothes by the top labels.

Youngblood is a team of superheroes formed by the United States government to be the next generation of heroes.