Ōnuma Quasi-National Park (大沼国定公園) is a 90.83 km2 quasi-national park on the Oshima Peninsula in southwest Hokkaidō, Japan. The park encompasses the volcanic Hokkaidō Komagatake (北海道駒ケ岳) as well as the Ōnuma (大沼) and Konuma (小沼) ponds, which abut against the west slope of the mountain. The park, which was designated as quasi-national in 1958, is the smallest major park in Hokkaidō. Ōnuma and Konuma were created when mudflows due to eruptions of Hokkaidō Koma-ga-take dammed up depressions at the base of the mountain. The ponds, which are dotted with watershields, are surrounded by birch and maple forests.

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