The original Goblin was Norman Osborn, a corrupt industrialist who cofounded a major technology firm with partner, Dr. Mendel Stromm. To seize total control, Osborn had Stromm framed for embezzlement and then searched his possessions, discovering a experimental intelligence enhancement formula. When Osborn attempted to create the serum, it turned green and exploded in his face. The accident changed Osborn, greatly increasing his intelligence and strength, but also drove him insane.
In his new madness, Osborn adopted the bizarre identity of the Green Goblin with the goal of becoming the Boss of organized crime. This was intended to be complemented by defeating Spider-Man, a notorious, but relatively low powered, opponent whom he was confident he could defeat to enhance his reputation. To this end, Osborn created a personal flying device, which started in a broomstick-like shape and evolved into his Goblin Glider, and personal weapons like grenades shaped as pumpkins, bladed projectile weapons called razorbats, and glove blasters which fired energy blasts from his fingers. Thus equipped, Osborn set out to achieve his twin goals, only to be frustrated at every turn by Spider-Man.
Frustrated, Osborn decided to lie low until he was sure his enemy's guard was down. When he was ready, Osborn arranged to have Spider-Man exposed to a special gas designed to suppress his spider sense. With that done, Goblin shadowed him until he learned Spidey's real identity of Peter Parker and then captured him. In turn, Osborn revealed his own identity to Peter and ranted about his origin and his intentions of killing his greatest enemy, before releasing Peter to do battle. Peter defeated Osborn, who lost his memory and had his costume destroyed by Spider-Man to eliminate his menace.
For a long while, the Goblin personality periodically re-emerged in Osborn to bedevil Spider-Man, only to be forced down in turn when he was defeated. Finally, the Goblin took control one final time and threatened Spider-Man's love, Gwen Stacy, by kidnapping her and taking her to the top of a bridge in New York City. In the resulting battle, the Goblin pushed Gwen from the bridge and Spider-Man's attempt to save her failed. With blood in his eyes, Spider-Man pursued The Goblin for revenge, but managed to control himself after defeating him in battle. In one final attempt to kill him, the Goblin tried to spear Spider-Man with his remote control glider, only to find himself impaled when Spider-Man avoided the attack. The Goblin was presumed dead for years.
As it turned out, Harold "Harry" Osborn, Norman's son and Peter's friend, saw the battle and took pains to cover up his father's Goblin identity and manner of death. Already mentally weakened with a serious bout with narcotics, he blamed Spider-Man for his father's death, and upon learning Peter's identity, planned his revenge as the second Green Goblin. Peter managed to subdue him in battle that left Harry in police custody where his claims of Peter Parker being Spider-Man were dismissed along with his claims of being the Green Goblin as the ravings of a man who was obviously insane. He was put under the medical care of Dr. Barton "Bart" Hamilton who managed to make Harry bury his vendetta and Goblin memories in his subconscious. Unfortunately, Dr. Hamilton gained the insane ambition of using Harry's secrets to gain the same power the Osborns had as the third Green Goblin. Eventually in his attempt, the underpowered amateur was killed and the Goblin menace was buried yet again.
Later, fashion designer Roderick Kingsley discovered an abandoned secret lair of Norman Osborn's and set about to discover the rest of Osborn's equipment and records. With much of that accomplished, Kingsley created a variant of the Goblin identity as the Hobgoblin, who plagued Spider-Man for months while manipulating innocents to hide his identity.
Still later, Harry's insanity relapsed and he became the Green Goblin again on numerous occasions until he died from the side effects of a modfied Goblin serum. His equipment and the identity of the Green Goblin was then briefly used by Philip Benjamin "Phil" Urich, who tried to gain a reputation as super-hero - though he sometimes seemed to be as maniacal as his villainous predecessors. When his equipment was damaged during a battle against a Sentinel in the Onslaught Crossover, Phil was unable to repair or replace it and the fourth Green Goblin had to retire.
Soon after that it was revealed that Norman Osborn is still alive and is determined to plague Spider-Man's life still more, but with a more subtle approach. For a while a genetic construct acted as the fifth Green Goblin, following Norman's orders, but it proved unstable and died. Currently, Norman still acts as the Green Goblin. Of all the Goblins, he has proved to be the most formidable and the most resourceful.
Recently, however, the Green Goblin's true identity was revealed to the public by a dedicated investigaton by The Daily Bugle. After a battle with Spider-Man and Luke Cage that spanned the length of Manhattan, he was arrested and sent to the jail for the first time in the character's 40 year history.