is a stratovolcano in the ancient province of Dewa (modern-day Yamagata prefecture) and the highest of the Three Mountains of Dewa. The Gassan Shrine stands at the mountain's summit, 1984 m above sea level.

The hike from its trailhead to the summit usually requires about 4-5 hours and can be challenging. Visitors should be aware of the weather and not try to hike