Gorr, the final survivor of his kind, endures a relentless existence on an unforgiving desert alongside his beloved daughter. In desperate need, he implores his god, Rapu, for assistance. However, tragedy strikes when his daughter succumbs to starvation. Just as Gorr begins to perceive a calling voice in the distance, he stumbles upon an oasis where he encounters Rapu, who has just slain the latest bearer of an ancient weapon called All-Black the Necrosword. Instead of offering help, Rapu ridicules Gorr’s plight, prompting a sense of betrayal that drives Gorr to seize the Necrosword and take Rapu's life—swearing vengeance on all gods.
Simultaneously, Thor is on a quest with the Guardians of the Galaxy, responding to various distress signals throughout the cosmos, all while attempting to regain his former fighting shape. Yet, deep down, Thor feels unsettled about his life and harbors thoughts of retirement. Reports regarding Gorr begin to pour in, including a warning from Lady Sif, who has been actively hunting him down. Alongside Korg, Thor parts ways with the Guardians to investigate Sif's dire message. They find her badly injured, her arm severed, as she warns them that Gorr plans to attack New Asgard.
In another storyline, Dr. Jane Foster, played by Natalie Portman, battles stage IV cancer. Despite her valiant efforts to find a cure, hope begins to fade. Yet, inspired, she travels to New Asgard in search of magical healing. In an unexpected turn, Mjølnir—a magical hammer enchanted by Thor during their time together—comes to life, fusing itself back together and granting Jane the powers of the Mighty Thor.
As night falls, Gorr unleashes chaos upon New Asgard, summoning shadow monsters using the Necrosword. Thor, Korg, and Sif confront these menacing creatures, joined by King Valkyrie and the newly empowered Foster. Despite their combative efforts, Gorr manages to kidnap the children of Asgard, including Heimdall's son, Axl Heimdallson. With a connection formed through Axl, Thor deduces that the children are trapped in the perilous Shadow Realm.
Understanding the gravity of the situation, Thor, Mighty Thor, Valkyrie, and Korg set off to Omnipotence City to seek assistance from Zeus. Skeptical of Gorr’s threat, Zeus captures Thor, forcing Valkyrie and Korg to intervene. In the chaos, Zeus uses his Thunderbolt to destroy Korg's physical form, leaving only his face intact. In his fury, Thor retaliates by fatally wounding Zeus with his own weapon. The group escapes, intent on confronting Gorr in the Shadow Realm.
On their journey, Thor uncovers Jane's tragic health condition and the couple rekindles their relationship. Upon arriving, they quickly realize they're walking into a trap—the very children they sought to save have led them into Gorr's snare. Gorr aims to confiscate Stormbreaker to wield the Bifrost Bridge and gain access to Eternity, where he can wish for the end of all gods. Yet again, Thor's team battles Gorr and his shadow minions but is forced to retreat to New Asgard after sustaining injuries.
Gorr's machinations continue to unfold as he opens the gate to Eternity using Stormbreaker. Thor arrives, imbuing the children with the power of Thor, helping them to fend off shadow monsters. With the tide of battle turning, Foster, despite her severe illness, bravely reclaims Mjølnir, joining the fight on Valkyrie's winged horse. In a climactic moment, she uses Mjølnir to shatter the Necrosword, sealing her fate alongside Gorr's as she ultimately succumbs to her ailment in Thor's embrace, transitioning to Valhalla.
Afterward, a statue of Foster as the Mighty Thor is erected in New Asgard. Sif and Valkyrie take it upon themselves to train the children, while Korg begins the process of regeneration as he contemplates fatherhood. In a heartwarming twist, Thor embraces his new role as the caregiver of Gorr's child, sharing Stormbreaker with her as he wields Mjølnir in battle. Together, they traverse the galaxy, earning the monikers of Love and Thunder.
In a mid-credits scene, Zeus, still nursing his wounds, dispatches his son, Hercules, to eliminate Thor. In a post-credits scene, Foster arrives at Valhalla, warmly welcomed by Heimdall as she steps into her afterlife.
