Jean Grey, one of the founding members of the X-Men, first appeared as Marvel Girl in The X-Men #1 (September 1963), created by Stan Lee and Jack Kirby. A mutant with powerful telepathic and telekinetic abilities, she was among Professor Charles Xavier's original students, alongside Cyclops, Beast, Angel, and Iceman. Throughout the 1960s and 1970s, Jean served as a core team member, developing a romantic relationship with Scott Summers (Cyclops) while gradually mastering her powers. Her significance escalated in the Phoenix Saga (*Uncanny X-Men* #101–108, 1976–1977), when a solar flare during a space shuttle mission nearly killed the X-Men; Jean absorbed the Phoenix Force to save them, emerging with vastly enhanced cosmic-level abilities and adopting the identity of Phoenix.
The early 1980s brought Jean Grey's most defining arc in the Dark Phoenix Saga (*Uncanny X-Men* #129–138, 1979–1980), written by Chris Claremont and illustrated primarily by John Byrne. Manipulated by Mastermind and corrupted by the Phoenix Force's immense power, Jean transformed into Dark Phoenix, committing galactic-scale atrocities, including the destruction of a populated star system inhabited by the D'Bari. Confronted by the X-Men and later tried by the Shi'ar Empire, she briefly regained control but chose self-sacrifice on the Moon, destroying herself to prevent further harm and marking one of the most tragic turning points in X-Men history.
Although presumed dead throughout much of the early 1980s, Jean's narrative evolved with later retcons establishing that the Phoenix entity had impersonated her during the Dark Phoenix events, while the true Jean lay in a healing cocoon at the bottom of Jamaica Bay. This revelation unfolded in the mid-1980s, culminating in her resurrection (*Fantastic Four* #286 and Avengers #263, both 1986) and reunion with the original X-Men to form X-Factor (*X-Factor* #1, February 1986). In this new team, operating publicly as mutant hunters while secretly aiding mutants, Jean grappled with her past trauma, rekindled her relationship with Cyclops, and solidified her enduring role as a cornerstone of Marvel's mutant mythology during the decade.