Hagurosan's Five-storied pagoda.

Dewa Sanzan (出羽三山) is in the northern Tōhoku region of the main Japanese island Honshu. Dewa Sanzan means "Three Mountains of Dewa" and indeed comprises the three sacred mountains of Mt. Haguro (羽黒山), Mt. Gassan (月山) and Mt. Yudono (湯殿山), clustered together in the ancient province of Dewa (modern-day Yamagata prefecture).

Understand

Holy to the Japanese Shintō religion and especially the mountain ascetic cult of Shugendō, Dewa Sanzan is a popular pilgrimage site visited by many, including famed haiku poet Matsuo Bashō on his Narrow Road to the Deep North. If you're lucky, you may even spot a yamabushi ascetic pilgrim blowing into a conch shell.

When to go

Mt. Haguro is accessible all year round, but Mt. Gassan and Mt. Yudono close during winter because of snow. The (short) peak climbing season lasts from July to mid-October. Festivals are held to celebrate the opening and closing of the shrines.

Get in

Regular buses from Tsuruoka (~40 min; ¥800) connect to Haguro-machi (羽黒町). The buses depart from the front of Tsuruoka Station -- there are other lines, so make sure to board the right bus. For the Mt. Haguro trail head, get off at the "Haguro Center" (羽黒センター) stop. The bus continues another 10 minutes to the summit of Mt. Haguro (羽黒山頂). See the Shonai Kotsu bus website has a bilingual page for services to Tsuruoka. After 15 minutes, the bus continues to Gassan Hachigōme (月山八合目), the trail head for Mt. Gassan. Check the bus schedule carefully -- there are special schedules during holidays. On the bus going from Gassan-Hachigōme back to Tsuruoka, change buses at the summit of Mt. Haguro. Occasional buses connect Yudono-san to Yamagata.

In Tsuruoka Station, the information desk can provide some basic information and a map of the Dewa Sanzan area, both in English. However, there are few other sources of information in English -- try to come with a Japanese speaker.

Get around

Buses shuttle from both the top of Mt. Haguro and the Kyuka-mura stop at the base of the mountain to Gassan Eighth Station. The bus stop is on the other side of the mountain (not in Haguro-machi), take the footpath down (40 min) instead of the road to get to the stop faster.

See and do

The traditional approach is to hike across all three mountains, although most visitors opt for a bus from Mt. Haguro to Mt. Gassan as the distance is quite long. You can leisurely climb up Mt. Gassan and come down via the Mt. Yudono in one day.

Mt. Haguro

Bashō commemorative stone.

Hagurosan is the most easily accessible of the three sites and the only one that can be visited without some hiking.

• The well-marked trail from the base of Hagurosan winds its way through the forest for a while, passing the beautiful wooden Gojū-no-tō (五重塔 Five-Story Pagoda) along the way. Built some 600 years ago, the pagoda is registered as a National Treasure.
• Soon the ascent of 2446 stone steps starts. Easy to walk and not particularly steep, the climb is tiring in its sheer relentlessness, but you can pause at a popular teahouse halfway up for refreshments and get a certificate of climbing up the hard way. This will take around one hour if you're in reasonably good shape and don't dally too much. You can also visit the place where Japanese Poet Bashō wrote one of his many famous poems. Turn right at the cross after the tea house (not up the steps). You will have to backtrack after visiting.
• Mt. Haguro (a mere 414 m) does not have an identifiable peak as such, at one point the trail simply flattens out and after a torī gate you will find yourself on the grounds of the shrine. The main attraction here is the Sanzan Gōsaiden (三山合祭殿), venerating the spirits of all three mountains.

Mt. Gassan and Mt. Yudono

Big gate at Yudonosan Jinja entrance.

The hike to the top of Mt. Gassan and across to Mt. Yudono is a relaxed full-day hike, thought it should be approached with due respect. Obtain a map of the area from any nearby tourist office before you set out and take heed of weather conditions. With a forecast of rain and without proper rain gear, hiking to the peak can be not only extremely uncomfortable (you will get soaked) but dangerous as well with high speed wind gusts, slippery rocks, and very cool temperatures near the top.

• Buses deposit passengers at Gassan Eighth Station (月山八合目, Gassan Hachigōme, ~1400 m), from where it's a fairly easy two and a half-hour hike 500m vertically up the mountain through rolling plains often shrouded in mist.
• The peak of Gassan (月山頂上, 1984m) features the simple Gassan Shrine (月山神社). Entry costs ¥500 but includes quick purification by the resident Shintō priest.
• If you continue the trail across the peak and down, keeping to the right when the trail splits, you will after 45 minutes encounter a last split where one trail continues up to the peak of Mt. Yudono (~1500 m).
• The real fun starts on the other trail to the right, which climbs down to Mt. Yudono Shrine (湯殿山神社 yudonosan jinja), which is considerably steeper and in places equipped with steel ladders to climb down, though most of these have been rebuilt. The time down from the trail split is one hour 20 minutes.
• The reward for your efforts is Mt. Yudono Shrine (湯殿山神社 yudonosan jinja), the holiest shrine of the three. Photography is prohibited and so is telling outsiders what you have witnessed - so Wikivoyage shall not spoil the surprise!
• The Mt. Yudono parking area and bus stop with a variety or eateries is only a short walk from the shrine.
• Buses departing Mt. Gassan and Mt. Yudono are few and far between, so plan your day accordingly. The last bus back to Tsuruoka train station leaves Mt. Gassan at 16:00 and Mt. Yudono at 16:30.

Ōami

You may want to stop by bus at Ōami and visit the Dainichibō Temple (大日坊) or the Chūrenji Temple (注連寺). To get there, take the Mt. Yudono leg bus and get off at Ōami. Unfortunately, bus schedules may not mesh well with various interesting temple tours.

• 1 Dainichibō Temple (大日坊), Ōami, Nyūdō−11 (backtrack to the street before the bus stop -- or, if you are at the bus stop, go to the street right of the vending machines -- and continue uphill for about 5 minutes; the temple entrance is a big gate). Offers a priest's remains and various other interesting trophies. English is not well spoken and no pamphlet is available. However, everybody will be nice and comforting while showing you around. 
• 2 Chūrenji Temple (注連寺), Nakadai-92-1 Ōami (continue the street following the bus, turn right at the big intersection and walk for about 20 minutes into the forest road to get to Chūrenji). Offers another Buddhist priest who starved himself to death while praying. Though this one is said to have been a criminal before becoming a priest. 

Buy, eat & drink

Bring plenty of water for Mt. Gassan and Mt. Yudono, as there is little to be had along the trail.

There is a source of drinking water in the descent to the Yudono Shrine, but you have virtually no chance of seeing it. It is hidden under a clump of grass along the river that you will cross on the way. The best chance to enjoy it is to stick to a group of Japanese pilgrims, from the junction between Mount Yudono and the descent to the sanctuary. There is a good chance that they stop at this place to fill up with water and eat a few things.

There are places to eat at the 8th and the 9th station and on the top of top of Mt. Gassan. Accommodation is also available at the 8th station and in a mountain hut near the Mt. Gassan summit; reserve in advance if you want to be assured a place for the night.

There is a small shopping center near the Mt. Yudono bus stop below the temple, which has a number of restaurants and many souvenir shops.

Sleep

Most pilgrims opt to stay in the town of Haguro-machi, at the foot of the mountain. There are over 30 shukubo here offering basic lodgings. Regardless of where you stay, though, you must arrive before the dinner hour or you will have a difficult time finding a room. The best way is to call in advance and make a reservation (in Japanese). The shokubo experience is a good way to enjoy the journey, provided someone in your party speaks Japanese.

• Saikan (斎館), ☏ +81 235 62-2355. Saikan is the sole pilgrim's lodging at the top of Haguro-san, left right before you pass under the torii. A fully equipped, large, impersonal, and beautifully placed ryokan with space for over 300 guests. Meals are a real treat as special monk food is served. Since the Saikan staff only speak Japanese, you can request that Japanese Guest Houses, a free service, help you arrange the reservation. Room with breakfast ¥7,000. 
• Hagurokan (羽黒館) (take the bus toward Haguro-machi, get off at Haguro Center, and walk down the road where the bus came from; where the road curves left, you can see this place's sign on the right). A recommended place to stay in Haguro.