Mount Ōyama, also Mount Afuri or Mount Kunimi, is a 1,252 metres (4,108 ft) high mountain situated on the border of Isehara, Hadano and Atsugi in Kanagawa Prefecture, Japan. Together with Mount Tanzawa and other mountains in the Tanzawa Mountains it forms the Tanzawa-Ōyama Quasi-National Park. Mount Ōyama is a popular sightseeing spot in Kanagawa Prefecture.
The mountain is made from non-alkali mafic rock. The rock is 7-15 million years old. The rock was extruded on the sea floor during the Neogene and then pushed up and onto the island of Honshu when the Izu-Bonin-Mariana Arc collided with the rest of Japan. Mount Ōyama has long been regarded as a holy mountain and object of worship. Religiously motivated mountain climbing has been practiced since the Hōreki era (1751–1764) and the various paths leading there were called Ōyama Kaidō. Today this name survives as the pseudonym of Route 246.