Akan Mashu National Park (阿寒摩周国立公園, Akan Mashū Kokuritsu Kōen) is a national park located on the island of Hokkaidō, Japan. Along with Daisetsuzan National Park, these are the two oldest national parks in Hokkaidō. The park was established December 4, 1934. Akan is an area of volcanic craters and forests, covering 90,481 hectares (904.81 km2). The park is famous for its crystal clear lakes, its hot springs, and its large marimo. It is the only place where marimo of appreciable size form naturally in Japan.