In the year 2154, humanity is divided into two starkly contrasting classes: the affluent, who enjoy a lavish lifestyle aboard a spacious Stanford torus-style space station known as Elysium, and the destitute residents of an overcrowded, decaying Earth. While Earth's inhabitants face stringent control from merciless robotic enforcers, the fortunate citizens of Elysium have access to advanced medical technology like the Med-Bays, which provide treatments to keep them free from disease and injury.
Among the downtrodden is Max Da Costa (Matt Damon), a former car thief now working at an assembly line for Armadyne Corp, a defense contractor that supplies weaponry to Elysium. An unfortunate incident at the factory exposes Max to a fatal amount of radiation, leaving him with merely five days to live. Meanwhile, a group of illegal immigrants from Earth attempts to breach Elysium’s defenses, prompting Jessica Delacourt (Jodie Foster), the Secretary of Defense for Elysium, to dispatch her brutal enforcer M. Kruger (Sharlto Copley) to shoot down the incoming shuttles. Despite her ruthlessness, Delacourt faces opposition from President Patel (Faran Tahir), who reprimands her actions and dismisses Kruger temporarily.
In her quest for power, Delacourt makes a deal with John Carlyle (William Fichtner), the CEO of Armadyne, to create a program capable of seizing control of Elysium's central computer, thereby allowing her to appoint herself as President. Carlyle, however, safeguards this critical information by uploading it directly to his brain, ensuring that it is heavily encrypted.
Desperate for a chance at survival through a Med-Bay, Max seeks the aid of the notorious smuggler Spider (Wagner Moura), with help from his friend Julio (Diego Luna). Spider agrees to assist Max, but only on the condition that he helps steal valuable data from Carlyle. Aware of Max’s dire health, Spider's medical team outfits him with a powerful exoskeleton to enhance his strength, alongside an implant that can store vital data. Together, they intercept Carlyle's shuttle, and although Max successfully downloads the critical information, the encryption renders it seemingly unusable.
In the shadows, Delacourt secretly orders Kruger to extract Carlyle and reclaim the valuable program. A violent confrontation results in the deaths of nearly all of Max's allies, and during the chaos, an injured Max seeks refuge with Frey (Alice Braga), a childhood friend who is now caring for her leukemia-stricken daughter, Matilda. Frey implores Max to take Matilda to Elysium for medical treatment, but he refuses, prioritizing his own escape. With Max's actions drawing scrutiny, Delacourt imposes a citywide lockdown to recover the stolen program.
Returning to Spider, Max learns that the data within his brain can grant citizenship to all Earth inhabitants—an idea that holds the key to his ultimate goal. Alas, the lockdown remains a barrier to any escape plan. In a twist of fate, Max negotiates with Kruger to secure a passage to Elysium, only to find that Frey and Matilda have been taken hostage.
As they ascend to Elysium, a fierce battle ensues aboard Kruger’s ship, leading to a crash landing. Max, Frey, and Matilda are apprehended by Elysium's forces. While the extraction team attempts to access the data within Max’s mind, they discover that doing so will result in his demise. Delacourt shows no mercy, opting to proceed regardless.
Amidst the chaos, Kruger undergoes a transformation in a Med-Bay, regaining his appearance and acquiring a military-grade exoskeleton. With a vengeance, he embarks on a rampage, eliminating the leadership of Elysium in his pursuit of power. Meanwhile, Max, Frey, and Matilda manage to escape confinement. Realizing that only Elysian citizens can utilize the Med-Bays, Max vows to use Carlyle's program to grant citizenship to everyone. He instructs Frey and Matilda to locate a Med-Bay while he pushes into the core of Elysium's data center, encountering Kruger once more.
In their final confrontation, Max manages to sever Kruger's connection to his exoskeleton, and in a desperate effort, Kruger attempts to take Max down with him. However, Max prevails, throwing Kruger to his demise as he races against time.
Max and Spider reach the core where they uncover the truth: activating the program will lead to Max's death. Knowing the stakes, Max speaks to Frey one last time through the radio before making the sacrificial decision to upload the program. As he breathes his final breaths, the data core reboots, instantly registering every Earth inhabitant as a citizen of Elysium.
Shortly after, President Patel, having broken into the core, finds Spider's status changed to that of a legal citizen, rendering the arrest order ineffective. Meanwhile, Matilda is healed by a Med-Bay, and Elysium's computer activates a fleet of medical ships to assist the newly recognized citizens of Earth, all thanks to Max's courageous sacrifice.
