The X-Men are a team of mutant superheroes, published in comic books by Marvel Comics. Over the decades, the X-Men have featured a rotating line up composed of a large number of characters.
Notation:
In 1986, The New Mutants briefly graduated to become the X-Men in Uncanny X-Men Annual #10.
In 1989, in the wake of the X-Men's "death" during "Fall of the Mutants", Banshee assembled a team of X-Men on Muir Island in Uncanny X-Men #254 to #255.
In 1994, to oppose the threat of the techno-organic alien Phalanx, a team of X-Men was quickly banded together in Uncanny X-Men #316.
In 1999, after Professor X disbanded the X-Men in an attempt to "smoke out" a Skrull impostor in their ranks, Cyclops and Jean Grey pulled together a team to help the Mannites in Astonishing X-Men, vol. 2 #1.
In 2001, after losing members when Storm started her X-Treme X-Men and Professor X was captured by Magneto, Jean Grey recruited a temporary team in Uncanny X-Men #392 in order to rescue Professor X.
In 2004, a team scratched together by Cyclops in the wake of Xorn's rampage through Manhattan, New York in New X-Men #149 to #150.
X-Men squad assembled from 2007 to 2014. Led by Cyclops with Wolverine serving as the field leader. Took on missions which required responses too violent or controversial for the X-Men to deal with directly. When Cyclops disbanded the X-Force, Wolverine put a new X-Force squad together without his knowledge.
In 2009, Beast gathered a scientific team in Uncanny X-Men #507 to attempt to deal with the mutant birth crisis and reverse the effects of M-Day. The team lasted until 2012.
In 2010, a team of the first mutants to surface in Earth since M-Day, tasked with rescuing and helping any other new mutants as they appear. The team lasted until 2012.