Thor: The Dark World is a 2013 American superhero film based on the Marvel Comics character Thor, produced by Marvel Studios and distributed by Walt Disney Studios Motion Pictures. It is the sequel to Thor (2011) and the eighth film in the Marvel Cinematic Universe (MCU). The film was directed by Alan Taylor from a screenplay by Christopher Yost and the writing team of Christopher Markus and Stephen McFeely. It stars Chris Hemsworth as Thor alongside Natalie Portman, Tom Hiddleston, Stellan Skarsgård, Idris Elba, Christopher Eccleston, Adewale Akinnuoye-Agbaje, Kat Dennings, Ray Stevenson, Zachary Levi, Tadanobu Asano, Jaimie Alexander, Rene Russo, and Anthony Hopkins. In the film, Thor and Loki (Hiddleston) team up to save the Nine Realms from the Dark Elves.

Development of a sequel to Thor began in April 2011 when producer Kevin Feige announced plans for it to follow the MCU crossover film The Avengers (2012). In July, Thor director Kenneth Branagh withdrew from the sequel. Taylor was hired to replace him as director in January 2012. The supporting cast filled out that August with the hiring of Eccleston and Akinnuoye-Agbaje as the film's villains. Filming took place from September to December 2012, primarily in Surrey, England, as well as in Iceland and London. Taylor wanted the film to be more grounded than Thor, inspired by his work on Game of Thrones (2011–2019). He hired Carter Burwell to compose the score, but Marvel replaced Burwell with Brian Tyler.

Thor: The Dark World premiered at the Odeon Leicester Square in London on October 22, 2013, and was released in the United States on November 8, as part of Phase Two of the MCU. The film was a commercial success, grossing over $644 million worldwide and becoming the tenth highest-grossing film of 2013. It received praise for the performances of Hemsworth and Hiddleston, visual effects, and action sequences, but was criticized for its generic villain and lack of depth. Retrospectively, Taylor expressed dissatisfaction with the film and said Marvel substantially altered it from his original vision during post-production. Two sequels have been released: Thor: Ragnarok (2017) and Thor: Love and Thunder (2022).