Lake Motosu (本栖湖, Motosu-ko) is the westernmost of the Fuji Five Lakes and located on the border of the towns of Fujikawaguchiko and Minobu in southern Yamanashi Prefecture near Mount Fuji, Japan.

[2] The remnants of the lava flow are now under the Aokigahara Jukai Forest, and there is evidence to indicate that these three lakes remain connected by underground waterways.

[1] The temperature of the water never drops below 4 °C (39 °F), making it the only one of the Fuji Five Lakes that does not freeze in winter.

[3] As with the other Fuji Five Lakes, the area is a popular resort, with many lakeside hotels, windsurfing facilities, camp sites, and excursion boats.

However, in recent years, reduced water transparency due to pollution from these activities has been a growing issue.