Onsen with a sauna in Gunma

Kusatsu · A sauna is available alongside the baths.

Takasaki · Recently renovated sauna facilities with two rooms (auto-loyly and self-loyly), widely praised.

Annaka · A sauna is confirmed by several reviewers.

Numata · A dry sauna (around 94C, 6-person capacity) is available.

Ota · Multiple sauna types including a barrel sauna and a Mongolian-style sauna, well regarded overall though loyly (steam pouring) is currently banned in the barrel sauna.

Shibukawa · A dry sauna running roughly high-80s C, holding up to about 10 people.

Numata · Sauna is confirmed by several reviewers, though one notes it gets very crowded (5 people packed in).

Shibukawa · A loyly-style sauna is available and generally regarded as comfortably hot rather than extreme.

Maebashi · Multiple sauna types exist (dry ~90C sauna, steam sauna, stadium sauna) with occasional löyly service.

Maebashi · A sauna is available alongside jet bath, jacuzzi, and cold bath.

Minakami · Has a distinctive low-temperature (~86C) 'bona sauna' with a view, well liked by sauna enthusiasts.

Katashina · A sauna running around 95C is available, small (about 6 person capacity).

Shibukawa · A well-regarded sauna (L-shaped, about 90°C, no loyly) plus an outdoor barrel sauna are frequently praised, but one reviewer reports being refused entry to the sauna area for lacking a swimsuit — a requirement not stated on the website.

Shibukawa · A small sauna is available.

Maebashi · A sauna is available and well-regarded, with good temperature and a water fountain nearby.

Takasaki · A sauna is available alongside the baths, confirmed by several reviewers.

Isesaki · Facility has two sauna rooms, mentioned across four reviews.

Isesaki · A large L-shaped high-temperature electric sauna seating 10+ people, mentioned repeatedly and positively.

Takasaki · An outdoor sauna (roughly 90C, 18-person) with TV is present, though it lacks sauna mats on some visits.

Ota · A far-infrared two-tier sauna plus a low-temp salt steam room are described by several reviewers.

Tomioka · A small sauna (fits about 5-8 people) is available and generally well-liked.

Annaka · A sauna is present, though descriptions vary between a small dry sauna near 90C and a mist sauna.

Maebashi · Two sauna types are available (dry sauna and steam/mist sauna).

Yoshioka · Three sauna types are available: high-temperature, medium-temperature, and steam/mist.

Maebashi · The sauna (including a salt sauna) is spacious and well-regarded, though it is also where regular-customer conflicts most often occur.

Isesaki · Several reviews describe multiple sauna rooms (dry sauna, löyly-style sauna) as a highlight.

Yoshioka · Has a sauna, though regulars often occupy it.

Maebashi · A sizeable sauna (10-20 person capacity) with TV is repeatedly confirmed, generally with auto-rolyu steam.

Kiryu · A self-service loyu (water-on-stones) sauna is popular with reviewers.

Tsumagoi · A sauna (including a pebble-floor variant) is present, but reviewers frequently measure it disappointingly low at 60-75C, though at least one visit found it appropriately hot.

Takasaki · A stove-heated sauna up to 96C with daily löyly sessions and a TV.

Minakami · A low-temperature (around 70C) far-infrared sauna is available.

Takayama · A sauna is available.

Maebashi · A sauna is consistently reported (80-90°C), though reviewers disagree on whether it feels small/cramped or large.

Numata · A large multi-tier sauna, reported temperatures roughly 80-100C, is a highlight of the facility.

Numata · Both a regular high-heat sauna and a weekend-only cypress-lined salt sauna are offered.

Kiryu · A dry sauna and an outdoor loyly (steam) sauna are both available, plus a paid private sauna room, though numerous reviewers complain that other bathers' poor sauna etiquette (loud talk, not toweling off, mat-hogging) ruins the experience.

Ota · A sauna is confirmed by many reviewers.

Annaka · A sauna exists but only operates weekends/holidays and shuts off as early as 17:00-18:00; one reviewer measured a low 76-78C and warned the resulting cold-plunge shock could be risky for elderly visitors.

Showa · A small sauna is mentioned by several reviewers, though it can be dominated by regulars and mismanaged etiquette.

Ota · A sauna is available.

Numata · A small dry sauna is on site, frequently described as cramped (fits only 2-3 people).

利根郡みなかみ町 · A mist sauna using the spring water is offered and mentioned by several reviewers.

Numata · Sauna is confirmed by many reviewers.

Maebashi · A sauna is available.

Minakami · A paid, wood-fired sauna is confirmed by most reviewers, though one visitor reported no sauna at all.

Ota · The facility has a small dry sauna (around 70C, five-person capacity), though it has been out of order on at least one visit.

Shibukawa · A sauna is present, described by several reviewers as small.

Katashina · A large sauna reaching roughly 93-100C is present, though some reviewers find it not very hot.

Tsumagoi · A sauna of decent size is present.

Midori · A sauna with automatic loyly (steam bursts), capacity around 10, running 96-98°C; a couple of reviewers complain the sauna floor mats are damp/smelly from infrequent changing.

Shibukawa · The affiliated hotel bath includes a sauna.

Nakanojo · A small one-person steam sauna exists beside the baths, though several reviewers found it cramped and unhygienic.

Naganohara · A sauna (and mist sauna) is available, confirmed by several reviewers.

Katashina · Has a sauna, though one reviewer found it old and left quickly.

Minakami · A sauna is available, with the women's side offering a mist sauna and a low-temperature sauna also present.