Jean Grey, one of the founding members of the X-Men, first appeared in The X-Men #1 (September 1963), created by Stan Lee and Jack Kirby. Initially known as Marvel Girl, she was depicted as a telekinetic mutant and the team's only female member in its early years, developing a romantic relationship with Cyclops (Scott Summers) while contributing to battles against threats like Magneto and the Sentinels. Her powers expanded dramatically in the 1970s with "The Phoenix Saga" (*Uncanny X-Men* #101–108), where she bonded with the cosmic Phoenix Force after a space shuttle accident, gaining immense abilities and adopting the Phoenix identity, culminating in the iconic "Dark Phoenix Saga" (*Uncanny X-Men* #129–137, 1979–1980), where corruption led to galactic destruction and her apparent suicide on the moon.
Retconned in the 1980s to reveal that the Phoenix Force had impersonated her while the real Jean healed in a cocoon, she returned in Fantastic Four #286 (1986) and helped form X-Factor. In the early 1990s, following X-Factor's reintegration with the X-Men, Jean wore a distinctive blue and orange costume designed by Jim Lee, featured prominently in X-Men #1 (1991)—the bestselling comic of all time—and popularized further in X-Men: The Animated Series. This era marked her as a core X-Men member on the Gold Team, exploring her powers without full Phoenix influence.
Jean Grey's later developments included reclaiming the Phoenix name in the late 1990s with a green-and-gold costume variation, marriage to Cyclops, involvement in major events like Avengers vs. X-Men (2012) where she briefly hosted the Phoenix again, death and resurrection in Phoenix Resurrection: The Return of Jean Grey (2017–2018), and ongoing explorations of her Omega-level status and Phoenix connection in series like X-Men Red and the 2024 Phoenix solo title, solidifying her as one of Marvel's most powerful and tragic figures.