In The Future, a beautiful astronomatrix named Barbarella (Jane Fonda
) floats through the galaxy in her spaceship, the Alpha-7. Suddenly she receives an urgent call on her monitor from none other than the President of Earth (Claude Dauphin
). He informs her that a young scientist named Durand-Durand went missing sometime during a mission to the North Star and is believed to have landed somewhere in the Tau Ceti star system. Not much is known about this region of space-- the President worries that Durand's invention, the positronic ray, may fall into the hands of a primitive culture; beings who might seek to use this technology as a weapon and launch an intergalactic war. Since the Earth, free of all conflict for centuries, lacks military and police personnel, the President tasks Barbarella with a mission to find the scientist. He teleports her some weapons and a device that will signal the presence of Durand-Durand. The latter has a "tonguebox" incorporated in its design which can translate any language.
Barbarella spends most of the journey to Tau Ceti in suspended animation. She awakens just in time to lose control of her spacecraft and crash land on Planet 16, which her spaceship informs her contains an atmosphere similar to Earth's. She changes into a new outfit to explore the arctic terrain. The first humanoids she meets are a pair of twin girls-- they jabber to her excitedly in a language she can't understand. Before she can adjust her tonguebox, one of them knocks Barbarella unconscious with a piece of ice. The girls then pull the dazed explorer along in their sled, which is attached to a manta ray-like creature that glides across the ice.
The girls arrive with Barbarella at the wreck of another craft where several other sets of twin children are sheltered and indigo-blue bunny rabbits abound. Barbarella recognizes the wreck as the Alpha-1, former spaceship of Durand-Durand. The children tie Barbarella to a post and bring out several mechanical dolls that walk towards her. It soon becomes apparent that the dolls all have sharp metal teeth and hinged jaws. They bite Barbarella while the children giggle gleefully, amused by their game.
Suddenly a man appears with several armored guards. He cracks a whip and captures the children in a net, then unties Barbarella. Once she gets her tonguebox working, she's able to understand him when he explains that he is a Catchman named Mark Hand (Ugo Tognazzi
) and that all children are sent away to the forests of Weir "until they've reached a serviceable age," at which point he captures them and brings them back to civilization. He offers Barbarella a ride back to her spaceship. When she asks how she can repay him, he tells her that he'd like to make love to her. Back on Earth, when people want to bond, erotically, they each take an exultation transference pill and press their palms against one another's. Barbarella is prepared to do this with the Catchman, but he's not interested in all that, he tells Barbarella that he wants to have sex on the bed in his snowship. She reluctantly agrees to do it the old-fashioned way, but soon discovers that she finds the experience quite enjoyable. The Catchman gives her a fur and repairs her spaceship, only when she tries to fly off, the ship's computer informs her that it's been repaired in reverse. She crashes back into the planet and quickly activates the ship's terra-screws so that she can tunnel through the planet's core.
She surfaces in the Labyrinth, amongst strange creatures including an "ornithanthrope," or angel, named Pygar (John Phillip Law
), who was blinded in the city of Sogo. Pygar takes Barbarella to visit Professor Ping (Marcel Marceau
) who explains that Pygar is aerodynamically sound, but lacks the morale to fly. Pygar, Professor Ping and all of the other unfortunates who roam the Labyrinth were imprisoned there by order of the Great Tyrant. They are not evil enough to be allowed to live in Sogo, the City of Night. Pygar takes Barbarella to his nest where they have sex. This restores Pygar's will to fly and Barbarella convinces him to fly them both to Sogo. Professor Ping meanwhile agrees to try and fix Barbarella's spacecraft.
As they fly over the Labyrinth, Barbarella and Pygar are attacked by several of the Great Tyrant's black guards, but they destroy them all. They enter the city where Pygar's wings attract immediate attention. He is abducted and Barbarella is cornered by a pair of ruffians who seem to have rape on their minds, but before they can lay a hand on Barbarella, they're both stabbed in the back by a woman with an eyepatch. The woman wants to "play" with Barbarella, but Barbarella rejects her advances and runs off to find Pygar.
She sees the angel up on another level of the city, drawing jeers from a mob. Shielding him from the mob, she tells Pygar to back up since there's a room behind them. The mob don't follow and Barbarella belatedly learns that it's because they've retreated into in the Chamber of Ultimate Solutions, which metes out various "exciting and surprising" forms of death. Before they're forced to choose one of the solutions, the Concierge of the Great Tyrant (Milo O'Shea
) enters and escorts them both out of the room. He explains that the silvery slime moving under the floor is the Mathmos, the life-force that sustains all of the evil in Sogo. Pygar is immediately swooped up in a net, while the Concierge pushes Barbarella down a chute. She emerges in the court of the Great Tyrant. The twin girls from Weir, Stomoxis and Glossina (Catherine Chevallier
and Marie Therese Chevallier
), clamor to play with Barbarella, but the Concierge scolds them to let their aunt, the Great Tyrant, have her turn first. Barbarella is soon granted audience with the Great Tyrant (Anita Pallenberg
) whom she recognizes as the "one-eyed wench" who rescued her earlier. The Great Tyrant drawls that she often likes to walk disguised among her people. She reveals that she's crucified Pygar and is holding him hostage so that Barbarella will play with her. Barbarella pretends to acquiesce but reaches under Pygar's loincloth and grabs a gun she'd stashed there. She threatens to shoot the Great Tyrant in the face unless Pygar is released. The Great Tyrant complies but her Concierge calls Barbarella's bluff when he notices that her power buckle is depleted. He suggests giving Barbarella "to the birds."
The Great Tyrant absconds with Pygar and attempts to ravish him, but he doesn't understand her demands for sex, stating that "An angel does not make love, an angel is
love." She sends him away to be devoured by the Mathmos.
Meanwhile, the Concierge locks Barbarella in a glass cage. It's empty at first, but soon fills with hundreds of finches and parakeets that peck her mercilessly. In the middle of this ordeal, a trap door opens up and she slides down a chute into the secret headquarters of the Resistance, led by one Dildano (David Hemmings
). Dildano informs Barbarella of his plans to overthrow the Great Tyrant by ambushing her while she sleeps in her Chamber of Dreams. He even possesses a key to this chamber, which is invisible. He asks Barbarella to help their cause and she agrees to do what she can once Professor Ping has fixed her spaceship. She offers to have sex with Dildano but he disdains sex, preferring to use the pill like a civilized Earthling. Barbarella reluctantly agrees even though they haven't exchanged psychocardiograms. After a session of hand-to-hand intercourse, Barbarella leaves the headquarters via another chute that deposits her somewhere else in the city. The Concierge finds her and takes her to his torture device, an organ-like machine that will cause Barbarella to die of pleasure. Barbarella's capacity for pleasure is so great that she breaks the machine, infuriating the Concierge. Just as the Concierge is deciding what to do with Barbarella next, her homing device begins to bleep, indicating that she is in the presence of Durand-Durand. Barbarella can't believe that the Concierge is the man she's been seeking; she was told that Durand-Durand was in his late twenties and the Concierge looks to be in his fifties. He attributes this to the lifestyle of pure evil he's been enjoying in Sogo.
When he learns that Barbarella has the key to the Great Tyrant's Chamber of Dreams, he confiscates her copy of the key, throws her inside the Chamber while the Tyrant sleeps, steals the Tyrant's key and seals them both inside. He plans to take over Sogo and enacts a coronation ceremony, but before he can be crowned, the city falls under attack by the Resistance. Durand-Durand uses the positronic ray to send the resistance fighters to the Fourth Dimension. However, the Tyrant unleashes the Mathmos, which consumes everyone else, including Durand-Durand. Only Barbarella and Pygar prove immune to the Mathmos, which cannot digest their goodness. Pygar takes Barbarella in one arm and the Great Tyrant in the other and begins to fly to safety. When Barbarella asks why he's saving the woman who tried to kill him and has destroyed the entire planet, he replies that "an angel has no memory."