Harry Osborn is perhaps Peter Parker's first true friend. His upbringing was radically different from Peter's as his life was rich in financial assets, but lacking the nurturing warmth of the Parker home. The son of the ruthless industrialist, Norman Osborn, founder of Osborn Industries and Oscorp, Harry lost his mother, Emily, before he turned one year old. Norman had little time for his son, and was frustrated by Harry's failure to demonstrate academic excellence or a competitive drive. Harry was unaware that his father had been permanently altered by a chemical explosion and had assumed a secretive criminal lifestyle as the nefarious Green Goblin.
Harry graduated from Standard High and, along with friend Gwen Stacy, went to Empire State University (ESU). There, Harry and Gwen became friends with Midtown High's star football player, Flash Thompson. Harry and Gwen also met studious Peter Parker, also from Midtown High, and misunderstood Peter to be a snob, due to urgent matters that prevented Peter from being friendlier. In time, the misunderstandings were forgiven, and Harry and Peter became friends. Harry invited Peter to move in to his apartment, rent-free thanks to his father's wealth. Peter was able to repay Harry by helping him as a tutor. While Harry and Gwen socialized with Peter and aspiring model Mary Jane Watson, Peter and Gwen began to date and fall in love. Mary Jane dated Harry, though she found flirting with Peter, the man she secretly knew was Spider-Man, irresistible. Mary Jane's antics infuriated Harry. With the pressure of school, his father's high expectations, and rejection from Mary Jane, Harry turned to illegal drugs. On a high, Harry told Mary Jane he forgave her for flirting with Peter, but she reacted indignantly and broke up with him. Harry initially blamed his breakup on Peter for stealing Mary Jane's attention from him. Peter found out Harry had overdosed on LSD, and sought medical attention. Peter then confronted and beat up Harry's drug pusher, delivering the message that he should never return. Norman, meanwhile, had recovered from an amnesiac state regarding his life as the Green Goblin, and clashed with Spider-Man. Spider-Man forced the Goblin to see his hospitalized son, snapping Norman out of his Goblin persona.
Harry returned home, in a fragile state, with Mary Jane's presence a burden on his heart. Norman once again became the Green Goblin, and killed Gwen Stacy. Witnessing his father's apparent death battling Spider-Man, Harry was driven to the brink of madness. While no one was watching, he removed his father's mask and costume before the police discovered the body. Harry held Spider-Man responsible for his father's death. Sometime later, Harry discovered his roommate's costume and secret identity. Insane and full of hate, he donned his father's costume and attacked Spider-Man as the new Green Goblin. With no superhuman powers, he was quickly defeated. Spider-Man removed the Goblin costume and paraphernalia from Harry before Harry was taken into custody. The police did not believe Harry's ravings that he was the Green Goblin since he looked too young. They therefore also did not believe Harry's claims that Peter was Spider-Man.
Harry was sent into psychiatric care under Dr. Barton Hamilton. Hamilton successfully cured Harry of his insanity, and induced him into forgetting about his life as the Goblin, and hence his knowledge of Spider-Man's secret identity. Harry returned home, and was reunited with his friends. He met Liz Allan, Peter's friend from Midtown High. The two began dating. Liz left for a short time, ashamed that Harry would not want to be with her after she was caught stealing for the sake of her step-brother, the Molten Man. Harry, however, accepted her when she returned to him.
Under hypnosis Harry had revealed everything about the Green Goblin to Dr. Hamilton. Coveting the Goblin's power, Hamilton eventually decided to become the Green Goblin himself. Taking Harry prisoner, Hamilton infiltrated New York's criminal underworld as the Goblin and subsequently encountered Spider-Man. Harry escaped captivity and also assumed the identity of the Goblin. Hamilton knocked Harry unconscious, but was then killed by the explosion of a bomb with which he had tried to kill both Harry and Spider-Man. Upon reviving, Harry had again lost the memory of being the Green Goblin, and Spider-Man's secret identity.
Soon afterwards, Harry became the successor to his father and president of Osborn Industries. He eloped with Liz Allan, and moved first to Long Island and then to a large house in Englewood, New Jersey, seeking a peaceful life. Harry and Peter drifted apart during this time, but were reunited by the return of the Molten Man and rise of the Hobgoblin (Roderick Kingsley) threatening the Osborn family with demands for his father's strength enhancing serum. After a difficult labor brought on by the trauma of facing the Hobgoblin, Liz gave birth to a son, Norman Harold Osborn, and asked Peter and Mary Jane to be the godparents. When the Parkers were evicted from their apartment, Harry and Liz took them in as tenants.
To defend his family from the Hobgoblin, Harry resumed his role as the Green Goblin. The stress began to take its toll, as Harry gradually lost mental stability again and returned to menacing Spider-Man as the Green Goblin. He kidnapped Mary Jane, and took her to the top of the Brooklyn Bridge where Gwen had died. Mary Jane refused to beg for her life, startling Harry to remember the love he felt for her, and promised that she and Aunt May would be kept safe in the war between him and Spider-Man. Harry remembered Peter's secret identity, and played mind games with Peter, making living in the apartment below the Osborns very uncomfortable. Hoping to get revenge on all those who had betrayed his father, Harry created the Norman Osborn Foundation, and invited his father's former associates together in one townhouse, wired to explode and kill them all. He enhanced his strength taking a version of the Goblin serum, and tried to kill Spider-Man once and for all. While Spider-Man and the Green Goblin traded blows, Mary Jane and Normie Jr. were inside the townhouse. Harry raced inside to save them before the building exploded. He succeeded; however, the new formula was a failure, poisoning him. In his final moments before death, Harry reverted back to being Peter's friend, and saved his life.
Before his death, however, Harry had planted a trap for Spider-Man whereby he funded the Chameleon to create life-models of Peter's parents. These replicas were so realistic, that they fooled Peter and his Aunt May. Spider-Man was emotionally devastated to discover the truth and Harry's involvement, and the replicas were destroyed. Sometime later, Spider-Man discovered within an abandoned Goblin warehouse a device which projected Harry's recorded memories into Peter's mind. Peter saw in his mind himself playing the roles of young Norman Osborn facing an abusive father as Harry had envisioned it, as well as recollections from Harry's youth. According to these recorded memories, unbeknownst to Norman, Harry had sabotaged the original Goblin formula, bitter at his father for consistently choosing work as a priority over his son.
Ex-Daily Bugle reporter Ben Urich chronicled the history of the Green Goblin in his book "Legacy of Evil" which Norman Osborn discredited. However, with Norman's identity publicly revealed, Urich's credibility has been restored.
In the aftermath of Spider-Man accepting an offer from Mephisto to save the life of his Aunt May in exchange for the elimination of his marriage from the timeline of history, Harry has somehow returned to life. Divorced from Liz and two others, he has returned from a years-long stay in a European rehab. He has no memory of being the Green Goblin, nor of Peter Parker's alter-ego. Harry is now the owner of a chain of cafes based on his old college hangout, the "Coffee Bean" and, while he considers Peter his best friend, he hates Spider-Man with a vengeance. He is currently dating Lily Hollister, friend of NYPD's forensic specialist Carlie Cooper and daughter of New York, District Attorney, Bill Hollister.
During the New York Mayoral Election, in the campaign headquarters of Bill Hollister, Harry stumbled upon Lily, while she was transforming from her alter-ego as Menace, the mysterious villain, who had been attacking the candidates for mayor. Harry was shocked, and upset with the incredible revelation, but he was even more fascinated to learn that Lily knew of his father's hidden labs and horrendous secrets. She revealed that while searching through the lab in New Jersey, she accidentally broke a vile containing the Goblin serum and it was absorbed into her skin, allowing her to transform into the Goblin, and not having the need for a mask. In an attempt to stop Lily, Harry donned the Green Goblin once again, and injected Lily with a serum that reversed the affects of the serum that she previously been exposed to.