After the death of his daughter Love and his pleas for help are ignored by his god, Rapu, Gorr is called to the god-killing weapon the Necrosword and uses it to kill Rapu, vowing to kill all gods.

Elsewhere, Thor parts ways with the Guardians of the Galaxy^{[N 2]} after receiving a distress signal from Sif. Upon arrival, a beaten Sif warns Thor of Gorr and that his next target is New Asgard. Dr. Jane Foster, Thor's ex-girlfriend who is diagnosed with terminal cancer arrives at New Asgard in hopes of seeking medical treatment. Thor's destroyed hammer Mjolnir reforges^{[N 3]} and bonds itself to Foster after years earlier Thor had unknowingly enchanted it to protect her. Thor arrives in New Asgard just as Gorr starts attacking the town with shadow creatures. He is surprised to find Foster with Mjolnir but nevertheless teams up with her, Valkyrie and Korg to fight Gorr. The group thwarts Gorr, but he escapes, kidnapping several Asgardian children.

The group travels to Omnipotent City to warn the other gods and ask for their help. The Olympian god Zeus is unwilling to help and has Thor captured, forcing the group to fight off Zeus's men. Zeus injures Korg; in anger, Thor impales Zeus with his own thunderbolt, which Valkyrie steals during their escape. They then travel to the Shadow Realm to save the children. However, this turned out to be a ruse for Gorr to take Stormbreaker, which he intends to use on the Bifrost to enter Eternity and ask for the destruction of all gods. Gorr manages to overpower Thor's group and successfully steal Stormbreaker. Gorr uses Stormbreaker to open the portal to Eternity. Valkyrie is badly injured and Foster ends the battle drained by her use of Mjolnir, with one more such use likely to hasten her death from cancer. Thor, therefore, goes alone, imbuing the kidnapped Asgardian children and their weapons with the power of Thor to fight alongside him. Foster joins Thor in fighting Gorr and destroys the Necrosword.

Admitting defeat, Thor manages to convince Gorr that all he wanted from Eternity was not to destroy the gods but to get his daughter Love back. Foster succumbs to her illness and dies in Thor's arms. Eternity allows Gorr's request to revive Love, whom he asks Thor to take care of before he dies from the effects of the Necrosword. The children return to New Asgard, where Valkyrie and Sif begin training them. Meanwhile, Thor, now in possession of Mjolnir again, continues to go on adventures to help people, with Love, now wielding Stormbreaker, by his side.

In a mid-credits scene, a recuperating Zeus sends his son Hercules to kill Thor. In a post-credits scene, Foster arrives at the gates of Valhalla, where Heimdall welcomes her.