Lagaan: Once Upon a Time in India, or simply Lagaan, (transl. Land tax) is a 2001 Indian Hindi-language epic period musical sports drama film written and directed by Ashutosh Gowariker. The film was produced by Aamir Khan, who stars alongside debutant Gracy Singh and British actors Rachel Shelley and Paul Blackthorne. Set in 1893, during the late Victorian period of British colonial rule in India, the film follows the inhabitants of a village in Central India, who, burdened by high taxes and several years of drought, are challenged by an arrogant British Indian Army officer to a game of cricket as a wager to avoid paying the taxes they owe. The villagers face the arduous task of learning a game that is alien to them and playing for a victory.

Produced on a budget of ₹25 crore (US$5.3 million), Lagaan was the most expensive Indian film at the time of its release. It faced multiple challenges during production: Khan was initially skeptical to star in a sports film, and later, prospective producers called for budget cuts and script modifications. Eventually, the film would become the maiden project of Aamir Khan Productions, and mark Khan's foray into film production. Gowariker was inspired by aspects of sports drama Naya Daur (1957) in developing the film. The language featured in the film was based on Awadhi, but was diluted with standard Hindi for modern audiences. Principal photography took place in villages near Bhuj. Nitin Chandrakant Desai served as art director, while Bhanu Athaiya was the costume designer. The original soundtrack was composed by A. R. Rahman, with lyrics written by Javed Akhtar.

Lagaan was theatrically released in India on 15 June 2001, clashing with Gadar: Ek Prem Katha. It received widespread critical acclaim for Gowariker's direction, Khan's performance, dialogues, soundtrack, and the film's anti-imperialist stance. With earnings of ₹65.97 crore (US$13.98 million) during its initial release, the film was the third highest-grossing Hindi film of 2001. Lagaan was screened at numerous international film festivals and garnered multiple accolades. It was the third, and as of 2024 the last, Indian film to be nominated for the Academy Award for Best Foreign Language Film after Mother India (1957) and Salaam Bombay! (1988). Lagaan became the most-awarded film at the 47th Filmfare Awards with eight wins, including Best Film, Best Director for Gowariker and Best Actor for Khan. At the 49th National Film Awards, the film won eight awards, including Best Popular Film.