In 2805, Earth is abandoned and covered in heaps of garbage left over from decades of mass consumerism facilitated by the megacorporation Buy ‘n’ Large (BnL). Seven hundred years earlier, BnL evacuated Earth’s population in fully automated starliners, leaving behind WALL-E trash compactor robots to clean the planet for humanity’s eventual return. The plan failed, however, and all WALL-E units are now inactive except one, which has developed sentience after decades of life experience. He manages to remain in operation by repairing himself using parts from other inactive units.
One day, WALL-E discovers a growing seedling. Later, a spaceship lands and deploys EVE, an advanced robot probe sent from the BnL starliner Axiom to search for vegetation on Earth. WALL-E falls in love with the initially cold and hostile EVE, who gradually softens and befriends him. When WALL-E brings EVE to his home and shows her his collection, she sees the plant, automatically stores it inside herself, and goes into standby mode waiting for her ship to retrieve her. WALL-E, confused why EVE seems to have shut down, tries numerous methods to reactivate her. When EVE’s ship returns and collects EVE, WALL-E clings to its hull and thus travels through space to the Axiom, which is hidden behind a nebula.
On the Axiom, the descendants of the ship’s original passengers have become morbidly obese after centuries of microgravity effects and relying on the ship’s automated systems for their every need, with their only way of movement being hovering chairs. The ship’s current captain, McCrea, leaves most of the ship’s operations under the control of its robotic autopilot, AUTO.
WALL-E follows EVE to the bridge of the Axiom, where the captain learns that by putting the plant in the ship’s holo-detector to verify Earth’s habitability, the Axiom will make a hyperjump back to Earth so the passengers can recolonize it. However, AUTO orders McCrea’s robotic assistant GO-4 to steal the plant as part of his own no-return directive A113, which was issued to BnL autopilots after the corporation concluded in 2110 that the planet could not be saved.
With the plant missing, EVE is considered defective and taken to the repair bay along with WALL-E for cleaning. WALL-E mistakes the cleaning procedure performed on EVE for torture and tries to save her, accidentally releasing a quarantined horde of malfunctioning robots. The on-board security systems then designate both WALL-E and EVE as “rogue robots”. Fed up with WALL-E’s disruptions, EVE takes him to the escape pod bay to send him home. There, they witness GO-4 disposing of the missing plant by placing it inside a pod which is set to self-destruct mode. WALL-E enters the pod to retrieve the plant, but GO-4 jettisons the pod into space. WALL-E escapes with the plant before the pod explodes and uses a fire extinguisher to propel himself back toward the Axiom, where he and EVE reconcile and celebrate with a dance in space.
When the plant is brought to the captain, EVE’s recordings of Earth are analyzed and the captain concludes that mankind must return to restore the planet. However, AUTO reveals his directive and stages a mutiny. When WALL-E tries to protect the plant, AUTO tasers and severely damages him. EVE realizes the only parts available to repair WALL-E are in his truck back on Earth. She helps him bring the plant to the holo-detector to activate the ship’s hyperjump. McCrea, fighting AUTO for control of the ship, manages to open the detector’s access hatch. AUTO partially crushes WALL-E by closing the hatch before McCrea, who was forced to walk after being incapacitated by AUTO, can finally disable the autopilot. EVE places the plant in the holo-detector, freeing WALL-E and instantly setting the Axiom to hyperjump to Earth.
Upon arrival, EVE rushes WALL-E back to his home where she repairs and reactivates him. However, his memory is erased and resumes his original programming as a waste compactor. Heartbroken, EVE gives WALL-E an electrical farewell kiss, which restores his memory and personality. WALL-E and EVE reunite as the humans and robots of the Axiom restore Earth and its environment.