Agatsuma Onsen
- Location
- Agatsuma, Gunma Prefecture, Japan
- Water type
- sulfurous
- Temperature
- 44 °C
- pH
- 6.5
Water profile
Relaxing — deep, immediate muscle release.
Rich in active gases or metals — a strong mineral character.
Soft water — natural, classic buoyancy.
Agatsuma Onsen is situated in Nakanojo Town, Agatsuma District, Gunma Prefecture, in the upper Agatsuma River valley — one of Japan's most concentrated hot spring corridors, leading from Nakanojo through the famous spa towns of Shima, Kusatsu, and Manza in a chain of geothermal activity driven by the Kusatsu volcanic system. The siliceous mineral waters here serve as an entry point to this extraordinary Gunma hot spring route, where the Agatsuma River valley's forested scenery, historic highway towns, and multiple onsen destinations make it one of the most rewarding natural and thermal tourism regions in eastern Japan. Nakanojo's connection to this famous onsen corridor, combined with the town's own Shima Onsen district known for its historic ryokan culture, makes Agatsuma Onsen part of one of Japan's most historically significant and geologically active hot spring landscapes.