In December 1929, World War I veteran Nick Carraway, undergoing treatment at a psychiatric hospital, tells his doctor about Jay Gatsby, the most hopeful man he ever met. The doctor suggests Nick tap into his passion and write down his thoughts, and Nick begins cataloging the events to his doctor.
Seven years earlier, in the summer of 1922, Nick moved from the Midwest to New York after abandoning writing. He rents a small groundskeeper's cottage in the North Shore village of West Egg, next to the mansion of Gatsby, a mysterious business magnate who often hosts extravagant parties. Nick has dinner with his beautiful cousin Daisy Buchanan and her domineering husband, Tom, at their mansion in East Egg. Daisy plays matchmaker between Nick and another guest, Jordan Baker, a famous golfer. When Nick returns home, he sees Gatsby standing by the harbor, reaching toward a green light coming from the Buchanans' dock.
Tom brings Nick to the Valley of Ashes, an industrial dumping site between West Egg and the city, and picks up his mistress Myrtle Wilson at a garage owned by her husband George. One day, Nick receives an invitation to one of Gatsby's parties. There, Nick encounters Jordan and they both meet Gatsby. Gatsby takes Nick to Manhattan for lunch, telling Nick on the way that he is an Oxford graduate and war hero from a wealthy Midwestern family. They go to a speakeasy, where Gatsby introduces Nick to his business partner Meyer Wolfsheim.
Jordan tells Nick how Gatsby, a Captain of the U.S. Army, started a relationship with Daisy in 1917 before the U.S. entered World War I, and is still in love with her; he throws parties hoping that Daisy might attend. Gatsby asks Nick to invite Daisy to tea. After an awkward reunion, Gatsby and Daisy begin an affair. Gatsby is dismayed when Daisy wants to run away with him, preferring that she get a proper divorce. He asks Nick and Jordan to accompany him to the Buchanan home, where he and Daisy plan to tell Tom that Daisy is leaving him. During the luncheon, Tom becomes suspicious of Gatsby and Daisy, but Daisy stops Gatsby from revealing anything to Tom and suggests they all go to the Plaza Hotel. Tom drives Nick and Jordan in Gatsby's car while Gatsby drives Daisy in Tom's car. Tom stops for gas at George's garage, where George tells him that he and Myrtle are moving and that he suspects Myrtle is unfaithful.
At the Plaza, Gatsby tells Tom of his affair with Daisy. Tom accuses Gatsby of having never attended Oxford and having made his fortune through bootlegging with mobsters. Eventually, both Gatsby and Daisy leave. After fighting with George over her infidelity, Myrtle runs into the street and is fatally struck by Gatsby's car after mistaking it for Tom's. Upon learning about Myrtle's death, Tom tells George that the car belongs to Gatsby and that he suspects Gatsby was Myrtle's lover, while Nick deduces Daisy was driving when the accident happened. Nick, overhearing Daisy accepting Tom's promise to take care of everything, tries to warn Gatsby about it, but the latter stubbornly believed that Daisy needs time to think about living with Gatsby.
Inside the mansion, Gatsby tells Nick the truth: that he was born penniless, his real name is James Gatz, and he had asked Daisy to wait for him until he had made something of himself after the war; instead, she married Tom seven months after the war ended. The next day, Nick goes back to work and Gatsby awaits a call from Daisy while swimming in his pool. The phone rings, and Gatsby's butler answers it. Believing the caller to be Daisy, Gatsby is shot and killed by a vengeful George, who then commits suicide. Nick, who was the one calling, hears the gunshots and is the only person other than reporters to attend Gatsby's funeral as Daisy, Tom, and their daughter are leaving New York. The media falsely and negatively paints Gatsby as Myrtle's lover and killer, enraging Nick. Disgusted with both the city and its inhabitants, Nick leaves after taking a final walk-through Gatsby's deserted mansion and reflecting on Gatsby's ability to hope.
In the sanatorium, Nick finishes typing his memoir and titles it The Great Gatsby.
