Lake Hyōko (瓢湖) is a 281-ha reservoir area in the city of Agano, Niigata, Japan. The reservoir was created in 1639 during the Edo period of Japanese history. It is noted for its abundant and diverse bird life, and is an important overwintering grounds for Whooper swans and Tundra swans. The area received protection from the Japanese government as a wildlife refuge in 2005. On October 30, 2008, it was registered as a Ramsar site.