As punishment for a past rebellion, each of the 12 districts of the nation of Panem is forced by the victorious Capitol to annually select two tributes, one boy and one girl between the ages of 12 and 18, to fight to the death in the Hunger Games. In District 12, Katniss Everdeen (Jennifer Lawrence) volunteers after her younger sister Primrose (Willow Shields) is initially chosen by lot. She and the male tribute, Peeta Mellark (Josh Hutcherson), are escorted to the Capitol by chaperone Effie Trinket (Elizabeth Banks) and their mentor Haymitch Abernathy (Woody Harrelson), a past District 12 victor, now an alcoholic. Haymitch impresses on them the importance of gaining sponsors, as they can provide gifts of food and supplies during the Games. During part of a series of televised interviews, Peeta publicly expresses his love for Katniss, which she initially takes as an attempt to earn sponsors for himself, though later learns that it could help her. While training, Katniss observes the Careers: Marvel (Jack Quaid), Glimmer (Leven Rambin), Cato (Alexander Ludwig), and Clove (Isabelle Fuhrman), tributes from Districts 1 and 2 who have been training for the Games from an early age.
At the start of the Games, Katniss ignores Haymitch’s advice and grabs supplies from the ground around the Cornucopia, a place filled with food, weapons and other supplies where the contestants start, and narrowly escapes being killed by Clove; more than half of the tributes are killed in the initial melee, and only 11 survive the first day. Katniss tries to stay as far away from the rest of the competitors as possible, but Head Gamemaker Seneca Crane (Wes Bentley) triggers a forest fire to drive her back towards the others. She runs into the Careers, with whom Peeta has seemingly allied, and flees up a tree. The Career pack fails to kill her and Peeta advises them to wait for her to come down.
The next morning, while the Careers and Peeta sleep, Katniss notices Rue (Amandla Stenberg), District 11’s young female tribute, hiding in an adjacent tree. Rue silently draws her attention to a nest of poisonous tracker jackers, genetically modified wasps that can cause hallucinations and death. Using a serrated knife, she cuts the branch holding the wasps, causing it to fall and release them onto the Careers. Peeta, Marvel, Cato, and Clove escape, while Glimmer succumbs to the venom and dies. Katniss is stung, and becomes disoriented from the venom, hallucinating the death of her father. After Rue helps Katniss recover from the poison, they become friends. Katniss devises a plan to destroy the cache of supplies that the Careers have been hoarding. After Katniss succeeds, Cato angrily kills a boy from District 3, since he had left pressure-sensitive mines around their supplies, which Katniss had blown up, thus destroying the supplies. Katniss discovers Rue caught in a trap and frees her, but not before Marvel finds them and kills Rue with a spear, and Katniss shoots him in the heart with an arrow, killing him. Katniss comforts Rue with a song and after she dies, the grieving Katniss places flowers around her body. She then holds three fingers up – a District 12 salute – as a way to honor Rue towards District 11 and to show a symbol of disgust towards the Capitol, infuriating the Capitol. The people of District 11 watch and then riot, leading President Snow (Donald Sutherland) to warn Crane that these Games are not turning out well.
Haymitch persuades Crane to change the rules to allow two winners if they are from the same district, suggesting that this will quiet the unrest. When this change is announced, Katniss searches for Peeta, finding him wounded after fleeing from the Careers. He tells her Cato found out that he was intending to return to Katniss, leading him to stab Peeta with a sword in his leg. After she moves him to safety, they hear an announcement that what each survivor needs the most will be provided at the Cornucopia. Despite Peeta’s strong opposition, Katniss leaves to get medicine for him. Clove attacks and pins her down; she then boasts about her part in Rue’s death. Katniss is saved when Thresh (Dayo Okeniyi), District 11’s male tribute, kills Clove to avenge Rue. He spares Katniss’s life — once — for Rue’s sake. The medicine heals Peeta.