In the year 2033, after a decade-long global drought in the wake of a comet striking the Earth, the little remaining water is controlled by Kesslee (Malcolm McDowell) and his Water & Power (W&P) corporation, which subdues the population by monopolising the water supply. Rebecca Buck – "Tank Girl" (Lori Petty) – is a member of a commune in the Australian outback that operates the last water well not controlled by the corporation. In an attack on the commune, W&P troops kill Tank Girl's boyfriend, Richard (Brian Wimmer), and capture Tank Girl and her young friend Sam (Stacy Linn Ramsower). Rather than killing her, Kesslee enslaves and tortures the defiant Tank Girl. Jet Girl (Naomi Watts), a talented but introverted jet mechanic who has given up trying to escape W&P, urges Tank Girl to make less trouble for their captors, though Tank Girl refuses. Among other forms of torture, W&P personnel push her down into a long pipe to induce claustrophobia.
The mysterious Rippers slaughter guards at the W&P compound, then escape. Kesslee uses Tank Girl to lure the Rippers into the open, but they gravely wound him. Tank Girl and Jet Girl escape during the attack. Jet Girl steals a fighter jet from W&P and Tank Girl steals a tank, which she modifies heavily. The girls learn from the eccentric Sub Girl (Ann Cusack) that Sam is working at a sex club called Liquid Silver. They infiltrate the club, rescue Sam from a pedophile, Rat Face (Iggy Pop), and then humiliate the club's owner, "The Madame" (Ann Magnuson), by making her sing Cole Porter's "Let's Do It" at gunpoint. W&P troops break up the performance and recapture Sam. Tank Girl and Jet Girl wander the desert and find the Rippers' hideout. They learn that the Rippers are supersoldiers created from human and kangaroo DNA by a man called Johnny Prophet. Tank Girl befriends a Ripper named Booga (Jeff Kober), while a Ripper named Donner (Scott Coffey) shows romantic interest in Jet Girl. Despite the objections of the Ripper T-Saint (Ice-T), who is suspicious of the girls, the Rippers' leader Deetee (Reg E. Cathey) sends the pair out to capture a shipment of weapons. The girls bring the weapons crates back, though most of them are empty. After finding Johnny Prophet dead in one of the containers, the girls and the Rippers realize that W&P has tricked them.
The girls and the Rippers sneak into W&P, where they are ambushed. Kesslee, whose body had been reconstructed by the cybernetic surgeon Che'tsai (James Hong), reveals that Tank Girl has unknowingly been bugged. Deetee sacrifices himself damaging the generator, and in the darkness the Rippers turn the tide of the battle. Jet Girl kills Sergeant Small (Don Harvey), who had earlier sexually harassed her. Kesslee reveals that Sam is in the pipe, her life endangered by rising water. Tank Girl kills Kesslee, then pulls Sam out of the pipe. The film ends with an animated sequence showing water starting to flow freely. Tank Girl drives down rapids, pulling Booga behind on water skis, then takes them over a waterfall, shouting for joy.
