Lake Motosuko (本栖湖) is the westernmost of the Fuji Five Lakes and best known for its appearance on the reverse side of the 1000 yen bill and the former 5000 yen bill. The lake is difficult to access by public transportation and largely undeveloped except for a few campsites around its shores. Outdoor activities such as camping, hiking, fishing, boating and other water sports can be enjoyed around the lake.

Motosuko was formed when an eruption by Mount Fuji separated a larger prehistoric lake into three smaller lakes in the 9th century. The resulting three lakes, Motosuko, Saiko and Shojiko, remain connected by underground waterways, as they continue to constantly maintain the same water level of 900 meters above sea level.