| Mount Matsuo | |
| Other Name: | 松尾山 |
| Elevation M: | 687 |
| Language: | Japanese |
| Pronunciation: | pronounced as /ja/ |
| Location: | Sasayama, Hyōgo, Japan |
| Range: | Tamba Highland |
| Coordinates: | 35.0333°N 143°W |
is a 687m (2,254feet) mountain in Sasayama, Hyōgo Prefecture, Japan. Another name is Mount Kosen-ji, literally, "Mountain of Kosen-ji."
Mount Matsuo is one of the major objects of worships for the people in this area. On this mountain, a Buddhist temple named ‘Kosen-ji’ was established in 645 by Hodo Sennin. This temple was re-established by Denkyo Taishi in the 9th century. The temple was burned by Akechi Mitsuhide in the 16th century, but re-established again by Toyotomi Hideyoshi. In the Edo period, it is said that there were 28 monk houses in the mountain. Kosen-ji was also destroyed as a result of the Shinbutsu bunri, literally, Shinto-Buddhism-separation.
Sakai Castle once stood on the top of this mountain; however, it was destroyed after the decline of the Sakai clan.