The were a population of nomadic mountain people who are believed to have once existed in Japan.
The Sanka had no permanent settlements, but lived in bands of wandering hunter-gatherers. They were known to sometimes visit villages to trade. It is unknown when and where the Sanka originated. suggested that they were the descendants of farmers or outcastes who fled into the mountains during long period of civil war in the 15th and 16th centuries. Until the Meiji period, the term was used by Japanese police in reference to itinerant or unemployed people regarded as likely to become criminals.
Early research on the Sanka was conducted by Yanagita Kunio in the 1910s. Around the same time, described the Sanka as being entirely criminal in character and a threat to national security. Yanagita criticized Takano's theory, saying that the proclivity for thievery associated with the Sanka came from "a difference in [their] conception of property".