Amemasu (雨鱒（アメマス）) or Ō-amemasu (大アメマス) is a giant whale- or fish-like creature from Ainu folklore. Some of the largest amemasu are said to live in Lake Mashū and Lake Shikotsu in Hokkaidō, with smaller ones inhabiting lakes throughout northern areas of Honshu. The amemasu are known for capsizing boats, creating earthquakes, and causing other natural disasters.