This is the story about the resilience shown by the Indians when they were under the British Rule. They are already taxed to the bone by the British and their cronies, but when Jack Russell announces that he will double the Lagaan (tax) from all villagers, they decide to oppose it. Leading the villagers is a handsome young man named Bhuvan, who challenges them to a game of cricket, a game that is to be played by veteran British cricket players, versus villagers, including Bhuvan himself, who have never played this game before, and do not even know a bat from a piece of wood. As the challenge is accepted, the interest grows and attracts Indians from all over the region, as well as the British from all over the country - as everyone gathers to see the 'fair play' that the British will display against their counter-parts, who are aided by none other than the sister, Elizabeth, of Captain Rusell.

Rahul Malhotra (Aamir Khan) is the manager of the heavily in debt family business. He is also the guardian of his dead sister's mischievous kids. Rahul hires Vaijayanti (Juhi Chawla) as governess. Vaijayanti is a runaway from home as she does not want to marry the man her orthodox family has chosen for her. Predictably, Rahul and Vaijayanti fall in love. Maya (Navneet Nishan), a rich girl in love with Rahul tries to ruin his family and his business, but all ends happily.

Ishaan Awasthi is an eight-year-old whose world is filled with wonders that no one else seems to appreciate; colours, fish, dogs and kites are just not important in the world of adults, who are much more interested in things like homework, marks and neatness. And Ishaan just cannot seem to get anything right in class. When he gets into far more trouble than his parents can handle, he is packed off to a boarding school to 'be disciplined'. Things are no different at his new school, and Ishaan has to contend with the added trauma of separation from his family. One day a new art teacher bursts onto the scene, Ram Shankar Nikumbh, who infects the students with joy and optimism. He breaks all the rules of 'how things are done' by asking them to think, dream and imagine, and all the children respond with enthusiasm, all except Ishaan. Nikumbh soon realizes that Ishaan is very unhappy...

Medical student, Sunita, is driven by curiosity to study the case of Sanjay Singhania, who is afflicted with short-term memory loss. She runs into him, befriends him, and finds out that he is out to kill a seemingly benevolent citizen, Ghajini Dharmatma. After warning the latter of the impending danger, she subsequently comes across a number of diaries written by Sanjay and attempts to put together a jigsaw puzzle as to how a successful and wealthy businessman became a crazed recluse, who re-lives his past through tattoos on his body, notes and Polaroid photographs on the wall of his Hiranandani Complex flat, and his sole obsession of carrying out his deadly mission - little knowing that Ghajini and his goons are out to erase every bit of evidence he has gathered and thus ensure that he ends up remembering nothing.

Farhan Qureshi and Raju Rastogi want to re-unite with their fellow collegian, Rancho, after faking a stroke aboard an Air India plane, and excusing himself from his wife - trouser less - respectively. Enroute, they encounter another student, Chatur Ramalingam, now a successful businessman, who reminds them of a bet they had undertaken 10 years ago. The trio, while recollecting hilarious antics, including their run-ins with the Dean of Delhi's Imperial College of Engineering, Viru Sahastrabudhe, race to locate Rancho, at his last known address - little knowing the secret that was kept from them all this time.

Ajay Rathore is a no-nonsense police officer from Mumbai Crime Branch. Long time ago his elder brother was killed by terrorists which caused him to quit his medical studies and join Indian Police Service. He is a great admirer of Pakistan-based ghazal singer Gulfam Hassan. During one of Hassan's concerts, they meet for the first time and become great friends. Meanwhile, Ajay's investigation into the Pakistan-supported cross-border terrorism takes him to Rajasthan and reveals an unsettling truth about someone close to his heart.

The biggest sporting event for the school town of Nainital is the annual cycling race. Schools and colleges here range from those like Rajput and Xavier's for the spoilt rich kids to local ones like Model for the poorer kids. For the past two years the cycling race has been won by the arrogant Shekhar Malhotra (Deepak Tijori) of Rajput College. Sanju (Aamir Khan) and Ratan (Mamik) are bothers who attend Model and run a small local cafe. Their father (Kulbhushan Kharbanda) is obsessed by the desire to see Ratan become the cycling champion. Ratan on his part is the ideal son and elder brother to Sanju, good in everything he does and has been the runner-up to Shekhar in the cycling race. Sunju on the other hand is a prankster, not taking life seriously at all enjoying life with his friends among whom is Anjali (Ayesha Jhulka) who loves him silently. Sanju however turns his attention on the new girl on the block...