2159.
Two classes of people exist: the very wealthy "Coordinators," people who can afford bio-genetical engineering, who live on an advanced space station called Elysium, built by the Armadyne Corporation; and the rest, who live on an overpopulated, ruined Earth. Secretary Rhodes (Jodie Foster), a government official, will stop at nothing to enforce anti-immigration laws and preserve the luxurious lifestyle of the citizens of Elysium.
Max (Matt Damon) is an ex-con who lives in Los Angeles and works in one of Armadyne's factories, that manufacture robotic surveillance drones. One day, Max is mortally wounded in an accident and seeks help from a powerful local crime lord (Wagner Moura) that has access to advanced medical technology stolen from Elysium. The crime lord tells Max that the only technology that can cure him is on Elysium, and he can help Max infiltrate the station if, in exchange, Max helps the crime lord to steal the security codes from Armadyne's CEO (William Fichtner), allowing the crime lord and his men to invade Elysium and take control of it.
Max agrees, and receives biotechnological implants that include a transmitter to steal the codes directly from the CEO's mind and transfer them to the crime lord's computer. Max then intercepts the CEO's spaceship as it is about to leave Earth for Elysium, and it eventually crash-lands. Max steals the codes, but learns that they were programmed with counter-measures if stolen, and will shut down his nervous system if he removes them from his own mind.
Max seeks his ex-girlfriend (Alice Braga) and learns that their daughter has Leukemia, which can only be treated aboard Elysium. Max then joins forces with his friend Julio (Diego Luna) to invade Elysium and lead all the people that were left behind there. Upon learning of this, Secretary Rhodes hires a mercenary (Sharlto Copley) to eliminate Max, but Max manages to kill the assassin after a drawn-out fight.
With the codes, the crime lord and his men enter Elysium and take control of it, stealing the power from Secretary Rhodes' hand. The crime lord then announces that all the illegal immigrants will be made into legal citizens and be transported to Elysium to leave in equal terms with the surprised Coordinators.