In Japanese folklore, mizuchi was a water dragon or serpent believed to inhabit rivers, lakes, and marshes.
The word mizuchi appears in early Japanese sources, including the Nihon Shoki, where it refers to a dangerous water creature. These beings were associated with drowning, waterways, and the hazards faced by people living near rivers. The term is sometimes translated as “water spirit,” “water serpent,” or “water dragon,” depending on the source and translation.
Mizuchi is distinct from Ryūjin, the dragon king of the sea in Japanese mythology. It is also different from the kappa, a more anthropomorphic river creature known in later folklore. Such distinctions matter because Japanese water beings vary considerably by region and historical period.
Modern retellings often use mizuchi as a general name for a Japanese water dragon, but older references do not always describe one single standardized creature with a fixed appearance.