The planet Mongo is on a collision course with Earth. Dr. Alexis Zarkov takes off in a rocket ship to Mongo with Flash Gordon and Dale Arden as his assistants. They find that the planet is ruled by the cruel Emperor Ming, who lusts after Dale and sends Flash to fight in the arena. Ming's daughter, Princess Aura, tries to spare Flash's life.
"The Tunnel of Terror"
Aura helps Flash to escape as Zarkov is put to work in Ming's laboratory and Dale is prepared for her wedding to Ming. Flash meets Prince Thun, leader of the Lion Men, and the pair return to the palace to rescue Dale.
"Captured by Shark Men"
Flash stops the wedding ceremony, but he and Dale are captured by King Kala, ruler of the Shark Men and a loyal follower of Ming. At Ming's order, Kala forces Flash to fight with a giant octosak in a chamber filling with water.
"Battling the Sea Beast"
Aura and Thun rescue Flash from the octosak. Trying to keep Flash away from Dale, Aura destroys the mechanisms that regulate the underwater city.
"The Destroying Ray"
Flash, Dale, Aura and Thun escape from the underwater city, but are captured by King Vultan and the Hawkmen. Dr. Zarkov befriends Prince Barin, and they race to the rescue.
Dale pretends to fall in love with King Vultan in order to save Flash, Barin and Thun, who are put to work in the Hawkmen's atomic furnaces.
Flash, Barin, Thun and Zarkov create an explosion in the atomic furnaces.
"Tournament of Death"
Dr. Zarkov saves the Hawkmen's city in the sky from falling, earning Flash and his friends King Vultan's gratitude. Ming insists that Flash fight a tournament of death against a masked opponent, revealed to be Barin, and then against a vicious orangopoid.
"Fighting the Fire Dragon"
Flash survives the tournament with Aura's help, after she discovers the weak point of the orangopoid. Still determined to win Flash, Aura has him drugged to make him lose his memory.
"The Unseen Peril"
Flash recovers his memory. Ming is determined to have Flash executed.
"In the Claws of the Tigron"
Zarkov invents a machine that makes Flash invisible. Flash torments Ming and his guards. Barin hides Dale in the catacombs, but Aura has her tracked by a tigron.
"Trapped in the Turret"
Aura realizes the error of her ways, and falls in love with Barin. She tries to help Flash and his friends to return to Earth — but Ming plots to kill them.
"Rocketing to Earth"
Ming orders that the Earth people be caught and killed, but Flash and his friends escape from the Emperor's clutches, and Ming is apparently killed in the flames of the "sacred temple of the Great God Tao". Flash, Dale and Zarkov make a triumphant return to Earth.
Early film fan historians have claimed that actor Lon Poff, playing the first of Ming's two high priests, died shortly after production began and so was replaced by Theodore Lorch. In fact, however, only Poff's character died, or rather was killed by Ming in an act of fury and replaced by Lorch's High Priest; but the scene was cut from the final print. Poff did not die until 1952.
According to Harmon and Glut, Flash Gordon had a budget of over a million dollars. Stedman, however, writes that it was "reportedly" $350,000.
Many props and other elements in the film were recycled from earlier Universal productions. The watchtower sets used in Frankenstein (1931) appear again as several interiors within Ming's palace. One of the large Egyptian statues seen in The Mummy (1932) is the idol of the Great God Tao. The laboratory set and a shot of the Moon rushing past Zarkov's returning rocket ship from space are from The Invisible Ray (1936). Zarkov's rocket ship and scenes of dancers swarming over a gigantic idol were reused from Just Imagine (1930). Ming's attack on Earth is footage from old silent newsreels, and an entire dance segment is from The Midnight Sun (1927), while some of the laboratory equipment came from Bride of Frankenstein (1935). The music was also recycled from several other films, notably Bride of Frankenstein, Bombay Mail, The Black Cat (both 1934), Werewolf of London (1935), and The Invisible Man (1933).
Crabbe had his hair dyed blond to appear more like the comic-strip Flash Gordon. He was reportedly very self-conscious about this and kept his hat on in public at all times, even with women present. He did not like men whistling at him.
Jean Rogers also had her hair dyed blonde prior to production, "apparently to capitalize on the popularity of Jean Harlow". Brunette was actually the natural hair color for both actresses.
Glenn Strange in uncredited roles wore the "Gocko" lobster-clawed dragon costume and also appears as one of Ming's soldiers.
Release and reception
Universal hoped to regain an adult audience for serials with the release of "Flash Gordon" and by presenting it in many of the top or "A-level" theaters in large cities across the United States. Various newspapers in 1936, including some not even carrying the Flash Gordon comic strip, featured half- and three-quarter-page stories about the film as well as copies of Raymond's drawings and publicity stills that highlighted characters and chapter settings.
The film was the first outright science fiction serial, although earlier serials had contained science fiction elements such as gadgets. Six of the fourteen serials released within five years of Flash Gordon were science fiction.
The serial film was subsequently released in a 72-minute feature version in 1936, which was reissued in 1949 as Rocket Ship. A different feature version of the serial, at 90 minutes, was sold directly to television in 1966 under the title Spaceship to the Unknown. For syndication to TV in the 1950s, the serial was renamed Space Soldiers, so as not to be confused with the newly-made, also syndicated TV series, Flash Gordon.
Flash Gordon was Universal's second-highest-grossing film of 1936, after Three Smart Girls, a musical starring Deanna Durbin. However, the Hays Office objected to the revealing costumes worn by Dale, Aura and the other female characters. In the two sequels, most of the female characters were thus dressed more modestly.
In his review of the film in the 2015 reference Radio Times Guide to Films, Alan Jones describes Flash Gordon as "non-stop thrill-a-minute stuff as Flash battles one adversary after another", and he states that it is "the best of the Crabbe trilogy of Flash Gordon films".