Lake Ashi (芦ノ湖, Ashi-no-ko), also referred to as Hakone Lake or Ashinoko Lake, is a scenic lake in the Hakone area of Kanagawa Prefecture in Honshū, Japan. It is a crater lake that lies along the southwest wall of the caldera of Mount Hakone, a complex volcano that last erupted in 1170 CE at Ōwakudani. The lake is known for its views of Mount Fuji, its numerous hot springs, historical sites, and ryokan. The lake is located on the Tōkaidō road, the main link between Kyoto and Tokyo. A number of pleasure boats and ferries traverse the lake, providing scenic views for tourists and passengers. Several of the boats are inspired by the design of sailing warships.
Visitors can also take the Hakone Sightseeing Cruise with its pirate ships from Togendai to Moto-Hakone Port and Hakone-Machi Port on opposite ends of the lake. The cruise line began in 1950.
The name means "lake of reeds" in Japanese: 芦 (ashi) is "reed", and 湖 (ko) is "lake". The abundance of nature makes it popular with hikers. There are many trails with different levels of challenge.