Thor is a 2011 American superhero film based on the comic book character of the same name published by Marvel Comics. It is the fourth film released as part of the Marvel Cinematic Universe. The film was directed by Kenneth Branagh, written by Ashley Edward Miller, Zack Stentz and Don Payne, and stars Chris Hemsworth, Natalie Portman, Tom Hiddleston, Anthony Hopkins and Stellan Skarsgård. The film tells the story of Thor, a god who is exiled from his homeland of Asgard to Earth. While there, he builds a relationship with scientist Jane Foster. However, Thor must stop his brother Loki, who intends to become the new king of Asgard.

Director Sam Raimi first developed the concept of a film adaptation of Thor in 2001, but soon abandoned the project, leaving it in "development hell" for several years. During this time, the rights were picked up by various film studios until Marvel Studios signed Mark Protosevich to develop the project in 2006, and the project was set up at Paramount Pictures. Matthew Vaughn was originally assigned to direct the film for a tentative 2010 release. However, after Vaughn was released from his holding deal in 2008, Branagh was approached and the film's release was rescheduled into 2011. The main characters were cast in 2009, and principal photography took place in California and New Mexico from January to May 2010. The film was converted to 3D in post-production.

Thor was released on April 21, 2011 in Australia and on May 6, 2011 in the United States. The film became a financial and critical success, grossing over $448 million worldwide and "Certified Fresh" by the review-aggregator website Rotten Tomatoes. The DVD and Blu-ray sets were released on September 13, 2011. A sequel, set for a July 26, 2013 release date, is in development.