Rikki-Tikki-Tavi is a short story in The Jungle Book (1894) by Rudyard Kipling about the adventures of a valiant young mongoose.

A 19th-century English family — who have moved to a bungalow in the jungles of Sugauli cantonment in Bihar State, India — discover a young mongoose half drowned from a flood. They revive it and decide to keep it as a pet. The young mongoose, named Rikki Tikki Tavi, finds himself confronted by two dangerous king cobras, Nag and his even more dangerous wife Nagaina, who had the run of the garden while the house was unoccupied. After the encounter with the cobras, Rikki's first true battle is with Karait, a dust brown snakeling who touchs the young boy Teddy. Although the snake, because of its deadly venom and small size, is an even more dangerous foe than a cobra, the mongoose kills it. The grateful family pet and praise "our mongoose".

After everyone is asleep, Rikki Tikki goes out for his nightly walk around the house and runs into Chuchundra the muskrat. Chuchundra pitifully and indirectly warns Rikki Tikki that Nag and Nagaina may be planning something terrible, after being told by his cousin Chua, the rat, who lives in the garden. Rikki Tikki hears a faint scratching sound that he knows to be Nag or Nagaina lurking around the bathroom sluice. He steals off to the bathroom and hears the cobras' whispering outside. At Nagaina's urging, Nag plans to kill the human family to empty the house so the cobras can again rule the garden. She also reminds him that their eggs, laid and hidden in the garden, would hatch soon (as they might the next day) and that their brood will need room and quiet. Nag goes to the bathroom to wait and kill the "big man", but Rikki follows and bites the cobra by the head above the hood. Nag thrashes about furiously, nearly beating Rikki Tikki to death. The noise wakes the man, who fires both barrels of a shotgun into Nag, blowing him in two pieces and almost hitting Rikki. Nag is then thrown on the rubbish heap, where Nagaina mourns for him and vows vengeance.

Rikki, well aware of the threat, tries to enlist the tailor bird Darzee, a "feather-brained little fellow", to distract Nagaina while he searches for her eggs, but is instead aided by Darzee's sensible wife. As Rikki finds and destroys most of the brood (biting off the tops of the eggs and crushing the young cobras), Nagaina corners the family at the breakfast table on the garden verandah ("they sat stone-still, and their faces were white") and threatens to kill Teddy with her venomous bite. Alerted by Darzee's wife, Rikki races to the veranda with the last egg in his mouth. His appearance distracts Nagaina long enough for the man to pull the boy to safety. Rikki Tikki provokes Nagaina into a final fight with neither opponent gaining the upper hand until Nagaina snatches the egg and flees to her hole, with Rikki in pursuit. The underground fight is not described, but after an agonizingly long time, Rikki comes out of the hole in triumph, having killed Nagaina. After this victory Rikki spends the rest of his days defending the family garden where no snakes dare to enter.