Mount Kujū (九重山, Kujū-san), located on the border of Kokonoe and Taketa in Ōita Prefecture, Japan, is a stratovolcano in Kyushu Island, Japan, with a summit elevation of 1,791 metres (5,876 ft). It is one of the 100 Famous Japanese Mountains. It is part of the Aso-Kujū National Park.

The Kujū range consists of a dozen or so volcanic bodies gathered in a region of 13 km east-west and 10 km north-south. The mountains in the range include:

• Kujū Mountains
  • Mount Kujū (1,787 m)- The main peak (久住山)
  • Mount Nakadake (1,791 m)- The highest peak in Kyushu
  • Mount Inahoshi (1,774 m)
  • Mount Hōsshō (1,762 m)
  • Mount Mimata (1,745 m)
• Taisen Mountains
  • Mount Taisen (1,786 m)
  • Mount North (Kita) Taisen (1,706 m)
  • Mount Heiji (1,642 m)

The Kujū volcanic group is mainly composed of andesite and dacite, which is defined as the volcanic activity above the Miyagi pyroclastic flow deposit which formed about 200,000 years ago. The north and south areas of Mt. Kujū are plateau grasslands whose main industry is dairy farming.

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  Mount Kujū from Mount Aso
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  Mount Iō from Chōjabaru
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  Mount Hōsshō and Mount Iō from Chōjabaru
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  Mount Kujū from Narukogawa Gorge
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  Mount Taisen
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  Kujū Flower Gardens and Kujū Mountains
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  Mount Kujū from Makinoto Pass with Mount Mimata on the right

• List of Ultras of Japan

• Kujusan - Japan Meteorological Agency (in Japanese)
• "Kujusan: National catalogue of the active volcanoes in Japan" (PDF). - Japan Meteorological Agency
• Kuju - Geological Survey of Japan
• "Kujusan". Global Volcanism Program. Smithsonian Institution. Retrieved 2021-06-25.