Mount Ōkueyama (大崩山), also known as Mount Ōkue, is a Volcanic Mountain on the Japanese island of Kyushu.

Part of an ancient volcanic formation known as the Okueyama Volcano-plutonic Complex,[1] Mount Ōkueyama (and possibly several nearby volcanoes)[2] experienced a massive eruption ~13.7 million years before present (13.7 Ma); it has been postulated that this eruption measured 8 on the Volcanic Explosivity Index, making the Ōkueyama eruption larger than any eruption in recorded history.

[2] The volcano is now considered to be extinct.

[1] In 1990, the area around the mountain was designated a Forest Ecosystem Reserve,[3] and In 2017 Mount Ōkueyama was declared part of a UNESCO biosphere reserve, the Sobo, Katamuki and Okue Biosphere Reserve.

[4][5] The area is managed by the Forestry Agency of Japan.