Harry Osborn was the son of wealthy industrialist Norman Osborn. When he was still a child, Harry had his soul bargained by his father with the demon Mephisto in exchange for making his financial life more successful. With the deal closed as a result of this bargain, Harry was destined to suffer numerous personal tragedies when he reached adulthood, and when he died, he would have his soul sent to Hell.
Harry grew up friends with Gwen Stacy at Standard High before going off to college. The two of them quickly befriended Flash Thompson when they arrived at Empire State University, but also adopted Flash's disdain for the reclusively scholarship student, Peter Parker, initially taking Peter's distant behavior as snobbery. However, he soon realized Peter was merely shy and distracted by his aunt May Parker's health problems.
Harry's relationship with his father was always strained, and it became worse when Norman secretly became the super-villain known as the Green Goblin. Harry and Peter Parker became closer as Peter consoled Harry over his father's distance, while Peter as Spider-Man was regularly fighting Norman as the Green Goblin. When Parker and Osborn learned each other's identities, Norman suffered amnesia after the fight, and Peter hid the Goblin costume for Harry's sake. He circulated a story that Norman Osborn was injured helping Spider-Man defeat the Green Goblin once and for all. Parker came to the hospital afterwards to check on Norman and make sure his amnesia held up. Harry misinterpreted this gesture as a sign of friendship, and things permanently thawed between Harry and Peter.
Harry and Peter became friends and started rooming together near campus. They began regularly seeing Gwen and Mary Jane Watson in group settings and on double dates, with Peter and Gwen, and Harry and MJ slowly becoming exclusive. Harry Osborn had hid himself away for weeks in order to grow his new "face fuzz". He would later shave it off. Harry's relationship with Mary Jane didn't sail smoothly, though. His relationship with his father began to degenerate again as Norman's memory returned, and Harry's trouble with pill addiction was too much for Mary Jane. She couldn't bring herself to stand by him as Harry was eventually hospitalized on an overdose. They reconciled when he got out, but only on the surface. When his father died in action as the Green Goblin after killing Gwen Stacy, Harry found the body and removed the costume. He refused to attend Gwen's funeral and chased away Mary Jane as he began to obsess over Spider-Man.
After learning that Peter was Spider-Man, Harry donned his father's costume and proclaimed himself the Green Goblin. He destroyed their apartment, and kidnapped Mary Jane, Flash and Peter's aunt May. When he was defeated by Spider-Man, he told everyone that Peter was really Spider-Man before being taken away, but this was dismissed as the ravings of a madman. He was taken to a medical institution and was released, suffering from amnesia, forgetting Spider-Man's identity and both his and his father's roles as the Green Goblin.
After being released and re-entering college, Harry moved in with Flash. He began seeing psychiatrist Bart Hamilton, who ended up using hypnosis to uncover the secrets of the Green Goblin from Harry's mind and donned the mantle for himself. Harry ultimately briefly became the Green Goblin again and battled Hamilton, who died in an ensuing explosion. Harry later married Liz Allan after they met at Ned Leeds' and Betty Brant's wedding. Harry and Liz had a son named Normie.
Harry's tranquility was shattered when the aftereffects of the Inferno crisis sundered the barrier between his conscious and subconscious minds, returning him his memories of being the Green Goblin as well as his irrational hatred of Spider-Man. Convincing himself that his father was a good person and that Peter resented the Osborns, Harry attacked him. As the Green Goblin, Harry subjected Spider-Man to a psychological torture using hallucinogens, although they also enabled his escape when he exploded in a fit of mindless rage. Tracking Spider-Man down, Harry decided to kill him. However, when Peter decided to let Harry deal a killing blow to end things once and for all, Harry found himself unable to deliver it. Conflicted, Harry fled with the promise of his eventual return.
Researching his father's chemical notes, Harry dosed himself with a new version of the Goblin Formula that his father had been working on before his death, which granted him superhuman strength but drove him further into madness. Harry kidnapped Liz, Normie and Liz's stepbrother Mark Raxton to announce his intentions to carry on the Green Goblin's legacy but without neglecting his loved ones. Lured to the reunion, Spider-Man confronted Harry and defeated him. Although Peter vouched for Harry to get psychological treatment from Dr. Ashley Kafka, authorities decided to transfer him to the Vault, a superhuman prison. However, lack of sufficient evidence saw the district attorney unable to put a case against Harry, in part because Liz was deep in denial and refused to testify against him, and he was released.
Harry began to hound Peter for days dressed as the Green Goblin, following him around the city and threatening to both reveal his secret identity and to kill him. As part of a plan to kill Norman's former associates, Harry publicized the gala opening for a new charity called the Norman Osborn Foundation, and rigged the building with explosives. When Peter decided to finally stop Harry, their fight took place in the rigged building. In an attempt to break the cyclical nature of their conflict, Harry injected Spider-Man with a paralyzing agent and decided to detonate the explosives so he and Peter could die together. Harry realized that both Mary Jane and Normie were in the building, and Peter spurred him on to save them. In a flash of sanity, Harry also returned for Peter and escaped with him before the building exploded. However, the experimental nature of the Goblin Formula in Harry's blood caused him to convulse moments later, and in his final moments of consciousness, he acknowledged Peter as his best friend. Harry was rushed to a hospital but died in the ambulance, holding Peter's hand.
Before his death, Harry created an artificial intelligence copied from his and his father's minds in order to carry on their legacy, and persuaded the Chameleon to create two robots who would appear to be Peter Parker's dead parents in an effort to get Peter to tell them who Spider-Man really was. Harry already knew Spider-Man's identity but wanted to mess with Peter's head so he convinced Chameleon that Parker, due to all the photos he had taken, was sure to know Spider-Man's identity. When Spider-Man discovered the fraud, he went briefly insane over the disappointment of losing his parents again. Harry also made an arrangement with Mendel Stromm to create a pair of test-tube-babies from Norman Osborn and Gwen Stacy's DNA, though the twins - Sarah and Gabriel Stacy - suffered from accelerated aging and clone degeneration, leading to Harry and the Osborn A.I. working to perfect the cloning process over numerous iterations. To further torment Peter, Harry also hired Mysterio to implant false memories of Gwen Stacy having had an affair with Norman while in Europe and giving birth to the twins in his father and Mary Jane Watson.Norman has later stated that when Harry created the twins, he was under the influence of Mephisto, the one who owned his soul.
A second artificial intelligence of Harry, taking the form of a hologram, was created by the Scriers to manipulate Normie Osborn into turning against his grandfather. This version refused to entertain the idea of Normie becoming a killer and declared the Osborn legacy would end with him. He assisted Spider-Man in defeating the Scrier leader before reassuring Normie that Spider-Man was not his enemy and thanking Peter for everything he'd done for him. When the badly injured Scrier grabbed Normie to kill him, the hologram Harry seemingly grabbed the Scrier from the shadows and finished him off. Spider-Man was left puzzled by these events.
As per the secret bargain Norman had made with Mephisto, Harry was sent to Hell following his death and was met by Mephisto, who mockingly informed him he'd been damned not only because of his father's deal but due to Harry not having warned Peter about his posthumous plots. Despite his protests, Harry's soul was tortured by demons with the appearance of his father for several years. During this time, the Osborn A.I. created a clone of Harry and Mysterio hypnotized Norman to implant false memories once again, this time to make him believe he had hired the Master of Illusion to fake Harry's death and subsequently sent him to Europe for rehab. Harry's clone eventually returned to America and replaced his genetic template as intended.
Sarah and Gabriel were later molded by Mephisto to act as his agents in a plot to destroy Spider-Man and adopted the shared moniker of Kindred. As part of their plans, Kindred used a shape-shifting serum provided by the Chameleon to impersonate Harry, pretending to be him returned from Hell. After Spider-Man sought out Doctor Strange's help to face Kindred, the Sorcerer Supreme confronted Mephisto, having noticed the demon's meddling in the wall-crawler's life. Betting on the outcome of Spider-Man's final confrontation against Kindred, Doctor Strange managed to free Harry Osborn's soul from the demon's grasp.
In the Legacy of Chris Thorndyke,
And he is reprised by Graham Phillips in the English dub and Kaito Ishikawa in the Japanese dub.