Rascal. Joker. Dreamer. Genius... You've never met a college student quite like "Rancho." From the moment he arrives at India's most prestigious university, Rancho's outlandish schemes turn the campus upside down—along with the lives of his two newfound best friends. Together, they make life miserable for "Virus," the school’s uptight and heartless dean. But when Rancho catches the eye of the dean's daughter, Virus sets his sights on flunking out the "3 idiots" once and for all.

The film begins in 1857, when India was ruled by the British East India Company. Mangal Pandey is a sepoy, a soldier of Indian origin, in the army of the East India Company. Pandey is fighting in the Anglo-Afghan Wars and saves the life of his British commanding officer, William Gordon. Gordon is indebted to Pandey and a strong friendship develops between them, transcending both rank and race.