Oyamatsumi no Okami is a mountain deity (yama-no-kami) in Japanese Shinto tradition, revered as the spirit governing mountains, and by extension associated with the sea and sake brewing in various local traditions. He is enshrined prominently at Oyamazumi Shrine on Omishima Island in Ehime Prefecture, a site historically linked to warriors and offerings for protection. Some regional traditions and shrine practices connect this deity to ancestral reverence and memorial rites, though such associations vary by locality and are not part of a single unified doctrine.