Peter Parker met Gwen while they were undergraduates at Empire State University. Initially, Peter's problems as Spider-Man made him ignore her advances, and in return, she felt insulted by his aloofness. Gradually, however, a romance developed. Gwen, a science major, seemed to appreciate Peter's intellectual personality, different from that of jocks like Flash Thompson and preppies like Harry Osborn. She was Peter Parker's first true love.
Their romance became more complicated when her father, Police Captain George Stacy, was killed by falling debris from a battle which involved Spider-Man and Doctor Octopus. Gwen blamed Spider-Man for that event, which set back their relationship for a while. Gwen left for Europe to deal with her loss.
Norman Osborn, the Green Goblin's alter ego, fathered twins, a boy and a girl, with Gwen Stacy, to whom she gave birth while she was in France. Feeling ashamed, she vowed that she would raise them with Peter. When she returned from Europe, Gwen and Peter resumed their relationship, but it would not last for long.
Soon after Gwen Stacy traveled to the Savage Land with both J Jonah Jameson and Peter in search of a monstrous man thing called Gog. She was kidnapped by the monster and Peter was believed dead but was rescued by Ka-Zar.
During this however, Gwen eventually comes to forgive Spider-Man and believe that he was not responsible for her father's death, and befriends middle-aged photographer Phil Sheldon who was searching for a way to clear the hero's name at the time.
Gwen Stacy was held on a bridge by the Green Goblin, who saw her and her children as a threat to his potential heirs. Spider-Man arrived to fight the Green Goblin, but Spider-Man was sick and not performing as well as usual. When the Green Goblin pushed Gwen Stacy off the bridge, Spider-Man caught her by a leg with a string of web. Unfortunately the sudden stop in midair snapped Gwen's neck, killing her. Spider-Man initially thought he had saved her, but when he pulled Gwen back up onto the bridge, he realized that she had died. In anger, Spider-Man almost killed the Green Goblin in retaliation, but chose not to do so in the end. The Green Goblin still seemingly died anyway when he was impaled by his own Goblin Glider in an attempt to kill Spider-Man (the Green Goblin was later discovered to have survived).
The death of Gwen Stacy had enormous repercussions. Mary Jane, a close friend of Gwen Stacy, was deeply affected by Gwen's death. Mary Jane became much more serious. Gwen's death also drew Peter and Mary Jane into a closer friendship, and eventually a romantic relationship. The Punisher tried to hunt down Spider-Man, as he wrongly believed Spider-Man to be Gwen's murderer.
The Punisher had been manipulated into going after Spider-Man by a supervillain called the Jackal. The Jackal was once Miles Warren, a former professor of Gwen, who had secretly been in love with her. Following her death, Warren grew increasingly insane and adopted the persona of the Jackal. He also became completely obsessed with Gwen and created a clone of her. The Green Goblin manipulated the Jackal and the clone of Gwen and used both of them in the Clone Saga. Eventually, the clone established her own identity.
Norman Osborn raised Gwen's two children, a boy and a girl Gwen had named Gabriel and Sarah, respectively. Due to Norman's enhanced blood, the twins aged faster than normal and became adults within the span of a few years. Osborn told them that Peter was really their father and was responsible for their mother's death.
The twins then attacked Spider-Man. Spider-Man told Mary Jane about his initial encounter with Gabriel and Sarah, whereupon Mary Jane revealed that she knew about Norman's involvement with Gwen and told all to Peter. She had kept it from him all these years because Gwen was distraught and begged her not to say anything. Peter told the twins the truth. Sarah believed Peter, but Gabriel did not. Gabriel took the Green Goblin formula and briefly became a new Green Goblin.
J.M. Straczynski stated that he originally wanted Peter Parker to be the father of Gwen's kids but the editors nixed the idea. The powers that be felt that it would age Peter Parker too much if he had two adult kids running around. It was then decided by the whole creative and editorial team that Norman Osborn would be the father.
The original comic featured a "snap" sound effect next to her head in the panel in which Spider-Man's webbing catches her. Some fans believe this indicates that her neck was broken by being caught by Spider-Man's web. Other fans do not think this sound effect implies this. Further confusing the issue, some reprints of the story take out the "snap" sound effect.
In Amazing Spider-Man #125 (October 1973), Roy Thomas wrote in the letters column that "it saddens us to have to say that the Whiplash effect she underwent when Spidey's webbing stopped her so suddenly was, in fact, what killed her. In short, it was impossible for Peter to save her. He couldn't have swung down in time; the action he did take resulted in her death; if he had done nothing, she still would certainly have perished. There was no way out." They also explained that Gerry Conway, Roy Thomas, and Stan Lee had decided that she had to die because Peter Parker wasn't ready for marriage, and the relationship was too often off and on again.
In an issue of What If?, Spider-Man saves Gwen not by letting her fall, but by leaping down in time to catch her - also, when the same is done to Mary Jane in the first Spider-Man movie, he swings down from his web to save her instead of trying to stop her in mid-air.
It is also interesting to note that Mayday Parker in MC2 does the same thing to save Gwen during a vision Gwen's death.
The Green Goblin's status in Spider-Man's rogues gallery was elevated by his murder of Gwen Stacy. Before the death of Gwen Stacy, Doctor Octopus had seemed to be Spider-Man's primary arch nemesis, but the death of Gwen Stacy was key to making the Green Goblin, even more than Doctor Octopus, Spider-Man's primary arch nemesis.
Several subsequent adventures have contained echoes of Gwen's death when other women have fallen great heights during Spider-Man's battles. On most occasions he has saved them by jumping after them and working with their momentum, rather than trying to stop them with his webbing.
In Marvel Knights: Spider-Man #12 a similar situation happens on the Washington Bridge, when the Green Goblin kidnaps Mary Jane this time. At one moment, Mary Jane falls from the bridge due the impact of a gun when she fired at Osborn. Then, Spider-Man states that he dreamed about Gwen's death and how he would stop it, and shoots many webs to brake Mary Jane's fall from many points, so her neck wouldn't break.
A discrepancy is established in the story "Spider-Man Revenge of the Green Goblin" (2002) that Norman Osborn believes he has no heir which "Sins Past" implies he has twin heirs. Osborn says "I have no heir, my son is dead...and my grandson Normie is much too young to carry on my stead".
Deadpool once had Arnim Zola make four Gwen Stacy clones in exchange for sparing his life.
In the House of M storyline, Gwen was never killed, and instead was married to Peter with a young son. The shock of having his true life's memories returned greatly devastated him. When the world was returned to normal by the Scarlet Witch at the conclusion of the story, Gwen remained dead and Mary Jane was again married to Peter.
Gwen was cloned in the third Clone Saga comic.
Gwen's death in Ultimate Spider-Man has provided similar controversy, as she was a much more developed character than her classic counterpart, and is generally seen as the most controversial and perhaps unnecessary move of the series. She was killed by the Carnage creature; however the bizarre, vampiric method of death and much of the Carnage creature in detail was never truly explained and could be a possible backdoor for her revival. See Gwendolyn Stacy (Earth-1610) for more information on her Ultimate universe counterpart.