When MI6 director M (Bernard Lee) receives a golden bullet engraved with "007", the service number of agent James Bond (Roger Moore), M identifies it as a gift from the world's most expensive assassin Francisco Scaramanga (Christopher Lee), called "the man with the golden gun" because of the golden gun and bullets he uses to kill his targets, and takes it as a warning that Bond is his next target. Consequently, M relieves Bond of his duties until the danger has passed. However, Bond decides to investigate Scaramanga himself and finds that he is not the target but that Scaramanga is trying to sell the Solex Agitator, a solar cell that can harness the sun's powerful energy, to the highest bidder.

The Man with the Golden Gun is loosely based on Ian Fleming's novel of the same name, published posthumously in 1965, a year after Fleming's death. It was adapted for the screen by American screenwriters Richard Maibaum and Tom Mankiewicz. The Man with the Golden Gun is the ninth film in the EON Bond series and the second movie to feature Roger Moore as James Bond. Little of the book's plot actually makes its way onto film, only the character names of James Bond, Mary Goodnight, M., and Scaramanga (but their characters are considerably different than in the book).

The Man with the Golden Gun is sung by Scottish singer Lulu. Interestingly, it is the only song in the series to mention Bond by name, though it happens in a later verse in the song that isn't included in the film version.

Bond starts out in London at MI6 headquarters. Most of the ensuing action then takes place in Southeast Asia. First, Bond travels to Beirut, Lebanon to recover the bullet that killed Agent 002. When the bullet turns out to be golden, it is confirmed that 002 was killed by Scaramanga. Then Bond is off to Macau (China) to talk to the weaponmaster who fashioned the bullet. When Bond witnesses a new shipment of bullets being picked up by Andrea Anders (Maud Adams), he follows her to Hong Kong. There, he witnesses the murder of Gibson (Gordon Everett), the scientist who developed the "solex agitator" that converts solar radiation to electricity and can prove to be an important step in reducing the world's reliance on fossil fuels and uranium. Assuming that Gibson was assassinated by Scaramanga and that Scaramanga was hired by rich entrepreneur Hai Fat (Richard Loo), Bond travels to Bangkok, Thailand to speak with Hai Fat. In the end, Bond ends up on Scaramanga's private island in the Yellow Sea within the boundaries of Red China.

According to dialogue in the film, China owns the island and leases it to Scaramanga in exchange for the occasional free assassination. The actual location of the archipelago that Scaramanga lives on is Khao Phing Kan and is in Phang Nha Bay on the western coast of Thailand. It is popularly called "James Bond Island" but that's not an official name.

Before defecting back to the British, Gibson worked for Hai Fat and built him a solar power plant based around his solex agitator. Scaramanga had gone into partnership with Hai Fat to get back the solex from Gibson. While working for Hai Fat, Scaramanga presumably "borrowed" men and equipment to build a second solar plant. Once the solex is put in place on his island and the plant is up and running, Scaramanga intends to ransom the technology to the highest bidder.

Of course, Scaramanga knows that Bond is on his way to the island even before Bond's hydroplane sets down. When Bond lands, Nick Nack (Hervé Villechaize) is there to meet him with a bottle of champagne. Like any good host, Scaramanga proudly shows Bond around the solar power plant that he "inherited" from Hai Fat and demonstrates how everything works, including a demonstration of how the solar collector can pinpoint the sun's rays to blow up things ...things like Bond's hydroplane. Later, Scaramanga, Bond, and Goodnight have a not-so-nice dinner together, and Scaramanga challenges Bond to a duel on the beach. Nick Nack counts to 20, Bond turns to fire, but Scaramanga has disappeared. Nick Nack leads Bond into Scaramanga's fun palace, telling Bond that he's on Bond's side because he will inherit Scaramanga's fortune if Bond kills him. Bond ends up killing Scaramanga by posing as a statue and, when Scaramanga wanders by looking for him, Bond shoots him. Bond and Goodnight then find each other, and Goodnight informs Bond that she knocked out the maintenance man, who fell into one of the liquid helium tanks. Bond tells her that his body temperature will raise the absolute zero temperature of the helium, causing the whole works to explode in five minutes. In their dash to find a way off the island, Bond confiscates the solex and Goodnight leads them to Scaramanga's yacht. As the island explodes, they head out to sea on autopilot, taking the moment to make love. Above them a panel opens up, and Nick Nack jumps down, intending to kill 007. Bond fights him off, eventually capturing him in a suitcase. Bond and Goodnight go back to what they were doing. Suddenly, the phone rings. It is M, wanting to speak to Goodnight. "Goodnight," says Bond as he replaces the receiver. In the final scene, the yacht sails on, and Nick Nack can be seen in a fishnet hanging from the mast.

Including The Man with the Golden Gun, Moore made seven movies in which he played James Bond: Live and Let Die (1973), The Man with the Golden Gun (1974), The Spy Who Loved Me (1977), Moonraker (1979), For Your Eyes Only (1981), Octopussy (1983), and A View to a Kill (1985).