Harold "Harry" Osborn is a supporting character in Marvel's Spider-Man. He is Mayor Norman Osborn's son who is terminally ill, unbeknownst to his best friends Peter Parker and Mary Jane Watson. Harry is voiced by Scott Porter.
Harry is the only son of Norman and Emily Osborn. His childhood was happy, although he suffered the loss of his mother at a young age due to complications from Oshtoran Syndrome.
Harry was a childhood friend of Peter Parker and Mary Jane Watson, which lasted into their adulthood. He graduated at the top of his class from Empire State University. At some point after this, he started an internship at Oscorp, hoping to eventually follow in his mother's footsteps as an environmental attorney.
However, he had inherited his mother's Oshtoran Syndrome and began to experience complications. Unwilling to put his friends through the hardship he felt during his mother's illness, Harry kept his condition a secret, pretending to be busy or hungover from partying when his sickness got in the way.
Eventually, Harry's condition became critical. His father had him directed to take an experimental medical treatment, which would take years for him to complete. Harry agreed to do so, leaving a note in his diary for Peter and Mary Jane should the treatment go wrong. Norman explained Harry's resulting absence to the world as Harry being in Europe managing Oscorp's international operations.
Before beginning the treatment, Harry left recordings for Peter at some of Oscorp's various research stations, which were set up by him to monitor air pollution in New York, a dream he carried out for his late mother. In these recordings, he asks Peter to finish what he couldn't. Following Norman's shutdown of Octavius Industries, Peter begins visiting the associated research stations to help his friend.
While breaking into Norman's apartment as part of a covert investigation, Mary Jane discovers the truth about Harry's condition, which she shares with Peter. She also finds journals he left behind which indicate that he knows his father loves him and is trying to help "in his own way" but is highly aware of just who his father is and how he operates. The journals also leave instructions that Peter and Mary Jane be told about his condition after he goes for treatment.
While it is unclear what the immediate results were of Harry's treatment, he can be seen at the conclusion of the game inside Norman's hidden lab, where he is kept in a holding tank in a clear green liquid with a black web-like substance clinging to him until a cure can be found for his condition. As Norman places his hand on the tank when he comes to visit him, the substance reacts and copies him, which Norman fails to notice.
Harry seems to be a selfless, intelligent, and good-natured man, hoping to follow in his mother's footsteps as an environmental attorney. Harry's recordings in his laboratories indicate that he is a kind individual with a strong sense of social conscience, sincere in his desire to continue his mother's legacy by cleaning up New York and making it a better place for his fellow man. He seems to have traits of the "lonely rich kid" trope, as Mary Jane recalls that in their childhood, Harry was noticeably more content watching cartoons in Aunt May's apartment than in his family's penthouse on an advanced TV.
Harry Osborn's first appearance was in Amazing Spider-Man #31 (December 1965).