| Mount Aka | |
| Other Name: | 赤岳 |
| Elevation M: | 2899 |
| Elevation Ref: | [1] |
| Prominence M: | 1916 |
| Listing: | List of mountains and hills of Japan by height Ultra |
| Map: | Japan |
| Map Size: | 260 |
| Label Position: | right |
| Translation: | Red Mountain |
| Language: | Japanese |
| Pronunciation: | pronounced as /ja/ |
| Location: | On the border of Chino, Hara of Nagano, and Hokuto of Yamanashi in Japan |
| Range: | Southern Yatsugatake Volcanic Group |
| Coordinates: | 35.9706°N 138.37°W |
| Type: | Stratovolcano |
| Volcanic Arc/Belt: | Northeastern Japan Arc |
is a 2,899m mountain on the border of Chino, Hara of Nagano, and Hokuto of Yamanashi in Japan. This mountain is the tallest mountain of Yatsugatake Mountains.
Mount Aka is a stratovolcano. This mountain is a center of the Yatsugatake-Chūshin Kōgen Quasi-National Park.
There are several routes to reach to the top of Mount Aka. The most popular route is from Minoto. It takes about four and half hours.