Mount Kōya (高野山, Kōya-san^?) is the name of mountains in Wakayama Prefecture to the south of Osaka. Also, Kōya-san is a modifying word for Kongōbu-ji (金剛峯寺). There is no one mountain officially called Kōya-san (高野山) in Japan.

First settled in 819 by the monk Kūkai, Mt. Kōya is primarily known as the world headquarters of the Kōyasan Shingon sect of Japanese Buddhism. Located in an 800 m high valley amid the eight peaks of the mountain (which was the reason this location was selected, in that the terrain is supposed to resemble a lotus plant), the original monastery has grown into the town of Kōya, featuring a university dedicated to religious studies and 120 temples, many of which offer lodging to pilgrims. The mountain is home to the following famous sites:

In 2004, UNESCO designated Mt. Kōya, along with two other locations on the Kii Peninsula, Yoshino and Omine; and Kumano Sanzan, as World Heritage Sites "Sacred Sites and Pilgrimage Routes in the Kii Mountain Range".

The mountain is accessible primarily by the Nankai Electric Railway from Namba Station (in Osaka) to Gokurakubashi Station at the base of the mountain. A cable car from Gokurakubashi then whisks visitors to the top in 5 minutes. The entire trip takes about 1.5 hours on an express train or 2 hours by non-express. Local automobile traffic can be very heavy on weekends until well into the evening. On weekdays however, the mountain offers a pleasant drive followed by the excitement upon reaching the monasteries lining the summit. Many Buddhist monasteries on the mountain function as hotels for visitors providing traditional accommodation with an evening meal and breakfast.