Jōshin'etsu-kōgen National Park, National park and biosphere reserve in Jōshin'etsu region, Japan.

Jōshin'etsu-kōgen National Park spans Gunma, Nagano, and Niigata Prefectures across about 148,194 hectares. It contains Mount Asama, the most active volcano on Honshū, and Mount Kusatsu-Shirane with its crater lake Yugama. The park's name combines the former provinces Kōzuke, Shinano, and Echigo with kōgen, meaning plateau.

Designated on 7 September 1949, the park initially covered the Mikuni range and Mount Asama. In 1956 the Myōkō-Togakushi area was added, and on 27 March 2015 that 39,772-hectare section became the separate Myōkō-Togakushi Renzan National Park. The name joins the characters for Kōzuke, Shinano and Echigo, the old provinces now Gunma, Nagano and Niigata.

The park's name is a kanji acronym of three former provinces: Kōzuke (上野, now Gunma), Shinano (信濃, now Nagano) and Echigo (越後, now Niigata), with kōgen meaning plateau. The Shiga-Kusatsu-Kogen Ridge Highway links the Yudanaka onsen area with Karuizawa, and the park's theme is 'a recreation world colored by mountains and plateaus'.

The park can be reached from several entry points, with Karuizawa station in the south offering direct Shinkansen trains from Tokyo. Visit in summer for hiking trails or winter for hot springs and snow activities, depending on your interests.

Mount Kusatsu-Shirane holds Yugama Crater Lake, with water acidity among the highest recorded in natural bodies worldwide. This extreme chemical environment creates a milky appearance and makes the lake one of the harshest volcanic lakes to find in nature.