In Canada, a young writer meets Pi Patel. The writer has been told that Pi’s life story would be a good subject for a book. Pi tells the writer the following story about his life:
Pi’s father names him Piscine Molitor Patel after the swimming pool in France. In secondary school in Pondicherry, he adopts the name “Pi” (the Greek letter, π) to avoid the sound-alike nickname “Pissing Patel”. He is raised in a Hindu family, but at 12 years old, is introduced to Christianity and then Islam, and decides to follow all three religions as he “just wants to love God”. His mother supports his desire to grow, but his rationalist father tries to secularize him. Pi’s family owns a zoo, and Pi takes interest in the animals, especially a Bengal tiger named Richard Parker. After Pi gets dangerously close to Richard Parker, his father forces him to witness the tiger killing a goat.
When Pi is 16, his father announces that they must move to Canada, where he intends to settle and sell the animals. The family books passage with the animals on a Japanese freighter. During a storm, the ship founders while Pi is on deck. He tries to find his family, but a crewman throws him into a lifeboat. A freed zebra jumps onto the boat with him, breaking its leg. The ship sinks into the Mariana Trench drowning his family. Pi briefly sees what appears to be a survivor, but it turns out to be Richard Parker.
After the storm, Pi awakens in the lifeboat with the zebra and is joined by a resourceful orangutan. A spotted hyena emerges from under a tarpaulin covering half of the lifeboat and snaps at Pi, forcing him to retreat to the end of the boat. The hyena kills the zebra and later the orangutan. Richard Parker emerges from under the tarpaulin, killing the hyena before retreating back to cover for several days.
Pi fashions a small tethered raft from flotation vests to which he retreats for safety from Richard Parker. Despite his moral code against killing, he begins fishing, enabling him to sustain the tiger as well. When the tiger jumps into the sea to hunt for fish and then comes threateningly towards Pi, Pi considers letting him drown, but ultimately helps him back into the boat. One night, a humpback whale comes too close to the boat, destroying the raft and its supplies. Pi trains Richard Parker to accept him in the boat, and realizes that caring for the tiger is also helping keep himself alive.
Weeks later they encounter a floating island of interconnected trees. It is a lush jungle of edible plants, freshwater pools and a large population of meerkats, enabling Pi and Richard Parker to eat and drink freely and regain strength. At night, the island transforms into a hostile environment. Richard Parker retreats to the lifeboat while Pi and the meerkats sleep in the trees; the water pools turn acidic, digesting the fish in them. Pi deduces that the island is carnivorous after finding a human tooth embedded in a flower.
Pi and Richard Parker leave the island, eventually reaching the coast of Mexico. Pi is saddened that Richard Parker does not acknowledge him before disappearing into the jungle. He is rescued and brought to a hospital. Insurance agents for the Japanese freighter company interview him, but do not believe his story and ask what really happened. He tells a different story, in which the animals are replaced by human survivors: his mother for the orangutan, an amiable sailor for the zebra, and the ship’s brutish cook for the hyena. In this story, the cook kills the sailor and feeds on his flesh. He also kills Pi’s mother after which Pi kills him with a knife and uses his remains as food and fish bait. The insurance agents are dissatisfied with this story, but they leave without questioning Pi further.
The writer recognizes the parallels between the two stories, noting that in the second version Pi is actually Richard Parker. Pi says that it does not matter which story is the truth because his family still died either way. He then asks which story the author prefers, and the author chooses the first, to which Pi replies, “and so it goes with God”. Glancing at a copy of the official insurance report, the writer reads aloud that Pi survived his great adventure “in the company of an adult Bengal tiger.”