- "Tailed beasts are spirits such as Shukaku and the Nine-Tails. They are essentially enormous clusters of chi and spiritual energy. During the great wars, each and every nation competed to get their hands on tailed beasts for military purposes. They did it be sealing the beasts into people."
- ―Chiyo to the rest of the Kazekage Rescue Team
The tailed beasts, also known as "chi monsters", are the nine titanic chi spirits created by the Sage of Six Paths out from the Ten-Tails during the Era of Raava. Sealed within humans by the nations of the world during the wars of the past, who thus are called Jinchuriki, they are distinguished by the tails in their backs, ranging from one to nine.