Only 22 nationwide, and the prefectures where you can reach them are limited. Includes wild baths with no lodging.
| Prefecture | Name | What kind of onsen | Annual Views |
|---|---|---|---|
| Gunma (Kanto) | Manza Onsen | At 1,800m elevation, tied with Nigorigo Onsen for the highest-altitude hot spring resort in Japan. Strongly acidic sulfur springs discharge 5.4 million liters a day from 27 sources. Also known as a ski resort in winter, though parts of the prefectural and national roads leading up to it close under snow each winter. | 16,818/yr |
| Tochigi (Kanto) | Santoya Onsen | A hot spring at about 1,460m on the flank of the Nasu mountains, reached by a 2–3 hour walk from the pass-side teahouse — a lone lodge with no road access, also known as a lamp-lit inn. | 12,800/yr |
| Gunma (Kanto) | Kirizumi Onsen | A secluded lodge, Kinyukan, in a remote valley within Joshin'etsu-kogen National Park, said to have been visited by historical figures such as Katsu Kaishu and Ito Hirobumi. | 11,753/yr |
| Gunma (Kanto) | Hoshi Onsen | Chojukan, the sole inn standing at 800m in Joshin'etsu-kogen National Park, famous for its mixed-bathing bath where spring water wells up directly through a floor of river stones — a hot spring dating to the Meiji era. | 8,291/yr |
| Gifu (Chubu) | Nigorigo Onsen | A mountain hot spring area at 1,800m on the 7th station of Mt. Ontake. Along with Manza Onsen, it is one of the highest-elevation hot spring areas reachable by car year-round, with several lone inns. | 8,137/yr |
| Nagano (Chubu) | Hakuba-Yari Onsen | At about 2,100m directly below Mt. Hakuba-Yarigatake in the Northern Alps, Japan's highest-elevation hot spring hut, reachable only on foot, with one of the largest natural spring flows in the country. | 6,275/yr |
| Hokkaido (Hokkaido) | Kamuiwakka Falls Onsen | A Shiretoko mountain stream that is itself a hot bath, its milky sulfurous water pouring into the waterfall pool. Since 2023, access has been limited to guided tours only. | 5,660/yr |
| Toyama (Chubu) | Takamagahara Onsen | Known as 'Japan's most remote hot spring,' located deep in the Northern Alps at the headwaters of the Kurobe River. Reaching it on foot from the nearest trailhead takes 2–3 days via mountain huts. | 5,535/yr |
| Akita (Tohoku) | Goshogake Onsen | A single lodge at roughly 1,000m elevation inside Towada-Hachimantai National Park, known for its geothermally floor-heated “ondoru” guest wing and its signature “hako-mushi” box steam bath, which envelops the body in natural volcanic steam. Unlike nearby Fukenoyu Onsen in the same Hachimantai area, it installed geothermal heating early on and remains one of the few mountain lodges here to stay open through the depths of winter. | 5,406/yr |
| Nagano (Chubu) | Honzawa Onsen | 'Unjo no Yu,' Japan's highest-elevation open-air bath at 2,150m, directly below Mt. Io in the Yatsugatake range. A 1–3 hour walk from the trailhead; past the forest-road gate no vehicle can enter, making it a true secluded hot spring. | 4,487/yr |
| Niigata (Chubu) | Renge Onsen | The lodge Renge Onsen Lodge sits at 1,475m northeast of Mt. Shirouma. Visitors can tour four rustic open-air baths scattered on the hillside behind it; it operates only during a limited season. | 4,147/yr |
| Yamagata (Tohoku) | Ubayu Onsen | A secluded inn in a ravine of the Azuma mountain range, said to have been discovered in the Kamakura period. Reached by an unpaved mountain road, it is known for its open-air bath enclosed by cliffs. | 3,947/yr |
| Iwate (Tohoku) | Toshichi Onsen | At 1,400m on Mt. Hachimantai, the highest hot spring inn in the Tohoku region. The lone inn, Saiun-so, is known for open-air baths overlooking a sea of clouds and Mt. Iwate, and closes in winter under snow. | 3,924/yr |
| Aomori (Tohoku) | Aoni Onsen | A single lodge deep in the Aoni Valley known as the 'Inn of Lamps' — the buildings use no electricity, lit only by oil lamps at night, and in winter guests can reach it only by the inn's own shuttle bus due to road closures. | 3,046/yr |
| Akita (Tohoku) | Fuke no Yu (Fukenoyu Onsen) | A lone inn at about 1,100m on Mt. Hachimantai, known for its mixed-bathing open-air baths made of wooden tubs, barrels, and rock pools. This remote mountain hot spring closes for winter under snow. | 2,864/yr |
| Yamanashi (Chubu) | Sanjo no Yu | A mountain-hut hot spring along the trail to Mt. Kumotori in Okutama, welling up in a valley at the headwaters of the Tama River, about a 3-hour walk from the end of the road. | 2,774/yr |
| Niigata (Chubu) | Akayu Onsen | A lone lodge along the hiking trail to Mt. Tairappyo and Mt. Senjokura, reached by about a 3-hour walk from the end of the forest road; a remote mountain hot spring requiring camping gear. | 2,772/yr |
| Hokkaido (Hokkaido) | Nakadake Onsen | A wild, unmanned hot spring along the pond-hopping trail of the Daisetsuzan Kogen area. There is no lodging; hikers reach this natural open-air spring only on foot. | 2,452/yr |
| Oita (Kyushu & Okinawa) | Hokkein Onsen | The highest hot spring in Kyushu, a mountain-hut bath in the Bogatsuru wetland of the Kuju mountain range. About a 2-hour walk from the Chojabaru trailhead, beloved by Kyushu hikers. | 2,288/yr |
| Fukushima (Tohoku) | Makukawa Onsen | Two inns tucked in old-growth beech forest along a forest road branching off the Bandai-Azuma Skyline at Tsuchiyu Pass. A waterfall lies about a 20-minute walk away; the inns close for winter. | 1,481/yr |
| Miyagi (Tohoku) | Yuhama Onsen | A lamp-lit inn tucked at 700m on the southwest foot of Mt. Kurikoma. It has no electricity, is a roughly 10-minute walk from the parking area, and closes for winter when the access road shuts. | 722/yr |
| Ishikawa (Chubu) | Iwama Onsen | An open-air bath about a further hour's walk along a streamside forest road from the lone inn Yamazaki Ryokan at the foot of Mt. Hakusan — the walk to the bath itself is the destination, not the inn. | 232/yr |