Jinchuuriki are humans that have tailed beasts sealed within them. They exhibit extraordinary powers due to the immense chakra reserves they possess.

A millennium ago, the world was terrorised by a rampaging, colossal monster known as the Ten-Tails. Eventually, through the combined efforts of the twin brothers, Hagoromo and Hamura Ōtsutsuki, the Ten-Tails was defeated and sealed within Hagoromo, becoming its jinchūriki.Throughout his travels, Hagoromo used the Ten-Tails’ power to perform many great deeds and promote peace during his lifetime, causing him to be revered as the “Sage of Six Paths”. Towards the end of his life, Hagoromo, knowing the Ten-Tails would be unleashed on the world again when he died, split its chakra into nine living entities called the tailed beasts.

Although humanity would for centuries exploit the tailed beasts as sources of power, it would not be until after the establishment of the hidden villages that the practice of creating jinchūriki resumed. The new hidden villages, each with their own tailed beasts, started sealing the beasts into selected villagers: in Konohagakure this was done to protect the village from its beast, the Nine-Tails; in Sunagakure, the abilities that manifested in their jinchūriki were studied so that non-jinchūriki could replicate them; more often than not, though, the jinchūriki were meant to be nothing more than military potential, with little regard for the jinchūriki or even the tailed beast.