Ryudo Dairyuo, whose name translates to "Great Dragon King," is a deity associated with dragon-kings (ryuo) revered in Japanese folk religion and Buddhist-Shinto syncretic tradition, particularly connected to the sea and waters upon which fishing communities depend. Dragon kings in this tradition are generally regarded as guardians of bodies of water, believed by practitioners to influence the seas, tides, and the safety of those who work upon them. Shrines and rites dedicated to such dragon deities have historically served coastal and fishing communities seeking favor for safe voyages and bountiful catches, though such benefits reflect devotional belief rather than verified historical fact.