A Kappa ('river-child'), alternatively called kawataro ('river-boy'), is a yokai (supernatural monster) found in Japanese folklore. The name is a combination of the word kawa (river) and wappa, an inflection of warabe (child). In Shint? they are considered to be one of many suijin ('water deities').

A hairy kappa is called a Hy?sube.There are more than eighty other names associated with the kappa in different regions. Along with the oni and the tengu, the kappa is among the best-known yokai in Japan.