Shirakoma Pond, Artificial pond in Sakuho and Koumi, Japan

Shirakoma Pond is a natural dammed lake at 2,115 m in the northern Yatsugatake mountains, on the boundary of Sakuho and Koumi in Nagano Prefecture. It covers 0.11 km², has a circumference of 1.35 km and a maximum depth of 8.6 m, with water clear to 5.8 m. The photograph shows a pebbly bed near the shore, a band of reddish-brown reflection at the far bank, and low wooded hills in autumn colors under a clear sky.

Shirakoma Pond formed when an eruption of Shirakoma Peak dammed the Ōishikawa River, creating a natural barrier lake at 2,115 m. It is Japan's largest natural lake above 2,100 m, with an area of 0.11 km² and a circumference of 1.35 km. The pond freezes over completely in late November, making it the earliest place in Honshu for lake skating. Its outflow supplies drinking water to the Saku region.

The pond's name comes from a local folktale in the Nanasaku Kōhi Densetsu-shū: a white horse led a woman who had followed her lover into the mountains to the water, and both vanished into it. The surrounding forest is registered by the Japanese Bryological Society as one of Japan's valuable moss forests, with many moss species growing on the trees and ground along the trail.

The pond lies in forest off National Route 299 (Mugikusa Pass), reached on foot via a promenade from the road. Paid parking lots run by the forestry cooperative sit on both sides of the road at the entrance, with a free small public lot near Mugikusa Hutte. Seasonal buses run to Mugikusa Pass from Saku-daira via Nakagomi and Yachiho, and from Chino. The area is designated a transport-difficult place by Japan Post, so mail cannot be sent here from outside.

The pond freezes over completely by late November, which is said to make it the earliest lake surface in Honshu where skating is possible. Its water is also unusually transparent, with visibility down to 5.8 metres and a maximum depth of 8.6 metres.