Ra.One is a 2011 Indian Hindi-language superhero film directed by Anubhav Sinha and produced by Gauri Khan under Red Chillies Entertainment. The film stars Shah Rukh Khan in a dual role and Arjun Rampal as the titular antagonist, with Kareena Kapoor, Armaan Verma, Shahana Goswami, Tom Wu, Dalip Tahil and Satish Shah in supporting roles. The name is inspired by Hindu mythological character Ravana. The film, Ra.One, a video game antagonist, escapes from the virtual world and arrives in the real world to hunt down Lucifer, the ID of Ra.One's creator Shekhar Subramaniam's son Prateek, as he had defeated Ra.One in a game. Shekhar gets killed by Ra.One, but Prateek resurrects G.One, the video game protagonist and Shekhar's lookalike, to defeat Ra.One and protect him and his family.

Principal photography began in March 2010 and took place in India and the United Kingdom and was overseen by an international crew. The post-production involved 3-D conversion and the application of visual effects, the latter being recognised as a technological breakthrough among Indian films. With a budget of ₹150 crore (equivalent to ₹309 crore or US$35 million in 2023), inclusive of publicity costs, Ra.One was the most expensive Indian film at the time of release, surpassing the ₹132 crore (equivalent to ₹296 crore or US$34 million in 2023) budget of Enthiran (2010). The producers spent ₹150 crore (equivalent to ₹309 crore or US$35 million in 2023), including a ₹52 crore (equivalent to ₹107 crore or US$12 million in 2023) marketing budget, which involved a nine-month publicity campaign, brand tie-ups, merchandise, video games and viral marketing. The film faced controversies involving plagiarism, content leaks and copyright challenges.

Ra.One was theatrically released on 24 October 2011, the beginning of the five-day Diwali weekend, in 2D, 3D and dubbed versions in Tamil and Telugu languages with three international premieres being held between 24 October 2011 and 26 October 2011. The film witnessed the largest international theatrical release for an Indian film as of 2011 and was preceded by high audience and commercial expectations. Upon release, Ra.One earned praise for the visual effects, action sequences, direction, music and the performances of Khan and Rampal, but criticism for the script. The film became the third highest-grossing Indian Hindi language film of 2011 domestically, the second highest-grossing Hindi film of 2011 worldwide, and broke a number of opening box office records. The film also earned more than ₹207 crore (US$24 million) worldwide against a budget of ₹150 crore (US$17 million), and was a commercial success. It subsequently won a number of awards for its technical aspects, notably one National Film Award, one Filmfare Award and four International Indian Film Academy Awards. While initially mixed around its time of release, the film's reception has improved over the years.