Thor Odinson is a fictional character portrayed by Chris Hemsworth in the Marvel Cinematic Universe (MCU) media franchise, based on the Marvel Comics character of the same name and the Norse mythological god of thunder. In the MCU, he is depicted as one of the most powerful Asgardians, an ancient alien civilization with long ties to Earth, who humans consider to be gods. Thor wields a powerful hammer called Mjolnir, and is initially depicted as the arrogant heir to the throne of Asgard whose brash behaviors causes turmoil among the Nine Realms under Asgard's protection. This brings him into conflict with his villainous adopted brother, Loki, the god of mischief.

Thor commits himself to the protection of Earth, and becomes a founding member of the Avengers. He eventually becomes the King of Asgard after Odin's death, but the entire realm is destroyed during the battle with his sister Hela. Thor then comes into conflict with Thanos, who slaughters half of the Asgardians and uses the Infinity Stones to erase half of the life in the universe before Thor himself kills Thanos. Thor later joins his fellow Avengers in obtaining the Stones from the past using time travel and they successfully undo Thanos' actions. When an alternate version of Thanos enters their timeline, Thor and the Avengers manage to defeat him. Thor then passes the crown of New Asgard to Valkyrie and joins the Guardians of the Galaxy for a brief time. Thor comes into conflict with Gorr the God Butcher and the Olympian god Zeus, while reconnecting with his terminally ill ex-girlfriend, the now Mjolnir-wielding Jane Foster. After Foster succumbs to her cancer to assist in Gorr's defeat, Thor adopts the latter's daughter, Love.

Thor is a central figure of the MCU, having appeared in nine films as of 2024^[update]. Thor's characterization and early films received mixed reception, however his storyline following Thor: Ragnarok (2017) was received much more favorably, with that film often being credited as revitalizing the character and his arc.

Alternate versions of Thor appear in the animated series What If...? (2021), with Hemsworth reprising the role. One version in particular, which depicts an alternate Thor raised without Loki who is recruited into the Guardians of the Multiverse by the Watcher in the battle against an alternate version of Ultron.

Thor was born approximately 1500 years ago to Odin, the King of Asgard, and Frigga. He was raised on Asgard as the crown prince, alongside his brother, Loki.

In 2011, Thor prepares to ascend to the throne, but Frost Giants attempt to retrieve the Casket of Ancient Winters, an artifact seized by Odin in a war centuries before. Against Odin's order, Thor travels to Jotunheim to confront Frost Giant leader Laufey, accompanied by Loki, childhood friend Sif, and the Warriors Three: Voltstagg, Fandral, and Hogun. A battle ensues until Odin intervenes, destroying the fragile truce between the two races. For Thor's arrogance, Odin strips his son of his godly power and exiles him to Earth. Odin casts an enchantment on Mjolnir, ensuring that only those who are worthy may wield the hammer. Thor lands in New Mexico, meeting scientist Dr. Erik Selvig, astrophysicist Dr. Jane Foster, and Foster's intern Darcy Lewis. Thor resigns himself to exile on Earth, where he develops a relationship with Foster. Odin enters the "Odinsleep", a period of rest needed to maintain his power, and Loki, having learned he is actually an adopted Frost Giant, seizes the Asgardian throne and prepares to conquer the Nine Realms. The Warriors Three and Sif find Thor, but the Destroyer attacks and defeats them, prompting Thor to offer himself instead. Struck by the Destroyer and near death, Thor's selflessness proves him worthy to wield Mjolnir. The hammer returns to him, restoring his powers and enabling him to defeat the Destroyer. Thor returns to Asgard and fights Loki before destroying the Bifröst Bridge to stop Loki's plans, stranding himself in Asgard. Odin prevents the brothers from falling into the abyss, but Loki appears to commit suicide when Odin rejects his pleas for approval. Thor makes amends with Odin, admitting he is not ready to rule.

In 2012, Odin sends Thor back to Earth using dark magic after learning Loki is alive and is attempting to conquer the Earth. He finds Loki on a Quinjet, held captive by Tony Stark, Steve Rogers, and Natasha Romanoff. Thor takes Loki away, hoping to convince him to abandon his plan. However, Stark and Rogers pursue Thor and after a brief confrontation, Thor agrees to take Loki to S.H.I.E.L.D.'s flying aircraft carrier, the Helicarrier. Agents including Clint Barton, who were mind controlled by Loki, attack the Helicarrier, disabling one of its engines in flight and causing Bruce Banner to transform into the Hulk. Thor attempts to stop the Hulk's rampage and both are ejected from the Helicarrier as Loki escapes. Thor then becomes a founding member of the Avengers upon returning to help Rogers, Stark, Banner, Romanoff, and Barton when Loki uses the Tesseract to open a wormhole over New York City to allow a Chitauri army to invade. Thor and the Avengers fight off the Chitauri and save the city. After Loki is defeated at Stark Tower, Thor returns to Asgard with Loki and the Tesseract.

In 2013, having used the Tesseract to rebuild the Bifrost and bring the Nine Realms to peace, Thor and his fellow warriors learn that the Convergence of the realms is imminent, with portals linking the worlds appearing at random. Heimdall alerts Thor that Jane Foster has left his near all-seeing vision, leading Thor to go to Earth. Jane inadvertently releases an unearthly force, and Thor returns with her to Asgard. Odin recognizes this force as a weapon known as the Aether, warning that it will kill Jane, and that its return heralds a catastrophic prophecy. The Dark Elves, led by Malekith, attack Asgard, searching for Jane. Thor's mother Frigga is killed protecting Jane, and Malekith is forced to flee. Against Odin's orders to stay in Asgard, Thor reluctantly frees Loki, who knows a secret portal to Svartalfheim, home of the Dark Elves, in return for Thor's promise to take vengeance for their mother. In Svartalfheim, Loki tricks Malekith into drawing the Aether out of Jane, but Thor's attempt to destroy the exposed substance fails. Malekith merges with the Aether and leaves in his ship as Loki is fatally wounded. Thor and Jane return to London through another portal. Thor ultimately defeats Malekith in a battle in Greenwich, and returns to Asgard to decline Odin's offer to take the throne, and tells Odin of Loki's sacrifice. Thor then returns to Earth and reunites with Jane.