Lake Saroma 100km Ultramarathon is a 100km ultra marathon in Saroma, Japan. Distance: 100km. Elevation: 300m D+. Difficulty: moderate (Challenge Rating 25/100). DNF rate: 12%. Time limit: 13h. Surface: road. Established 1986.
Lake Saroma 100km Ultramarathon
Saroma, Hokkaido, Japan
"100km around Lake Saroma in cool Hokkaido. One of the fastest 100km courses on Earth."
Japan's premier road 100K — a flat, fast course around Lake Saroma in Hokkaido that consistently produces world-class times.
The Course
A fast, flat point-to-point road ultra around the shores of Lake Saroma in Hokkaido. The course follows quiet roads through fishing villages, flower fields, and along the lake shore. Famous for producing fast times.
flat
point-to-point
12
Runner Experience
Solid aid station network with 12 stops along the course. Standard ultra fare — food, electrolytes, first aid.
Warm, inclusive finish line with a strong community feel. Runners celebrate together regardless of finish time.
Race Day Weather
15°C
10° – 20°
70%
25%
Hokkaido summer — cool and pleasant compared to mainland Japan. Occasional fog from the Sea of Okhotsk.
Stats & Records
1986
2,500
11:00:00
06:09:14
Nao Kazami (2018)
06:33:11
Tomoe Abe (2000)
Entry
¥15,000
January
instant
Lore & Trivia
Lake Saroma 100K is Japan's most prestigious 100km race — a flat, fast course around Lake Saroma on Hokkaido's northern coast. The race has produced some of the fastest 100km times in the world, attracting elite Japanese runners who specialise in the distance. Japan's 100km running tradition is distinct from Western ultrarunning — more road-focused, more tactical, and rooted in a culture that values precision and consistency over adventure.
- ▸ Lake Saroma is one of the fastest 100km courses in the world — the flat terrain produces incredible times.
- ▸ Nao Kazami's 6:09:14 is the Japanese 100km record, set on this course.
- ▸ The race is so popular in Japan that it requires a lottery with over 10,000 applicants for 3,500 spots.
- ▸ Hokkaido's cool summer temperatures make this ideal for fast road ultra performances.
- ▸ The course passes fields of lavender and wildflowers in full bloom.
Saroma is Japan's premier 100K — flat, fast, and the perfect test of pace discipline on the Hokkaido coast.
Compare with another race
Similar Races
2 MAY 2026
Ultra-Trail Mt. Aso Round Trail
Aso, Japan
6 MAY 2026
Shiga Kogen Extreme Trail
Shiga Kogen, Japan
24 APR 2026
Ultra-Trail Mt. Fuji
Kawaguchiko, Japan
24 APR 2026
Ultra-Trail Mt. Fuji
Kawaguchiko, Japan
Frequently Asked Questions
How long is Lake Saroma 100km Ultramarathon? +
Lake Saroma 100km Ultramarathon is a 100km (100km) ultra marathon with 300m of elevation gain. The course is point-to-point on road terrain.
How hard is Lake Saroma 100km Ultramarathon? +
Lake Saroma 100km Ultramarathon is rated moderate with a Challenge Rating of 25/100 (Moderate). The DNF rate is 12%. Runners have 13 hours to finish.
How do I enter Lake Saroma 100km Ultramarathon? +
Entry is by lottery. Entry costs ¥15,000. with a maximum of 3500 starters.
What is the weather like at Lake Saroma 100km Ultramarathon? +
Average temperature is 15°C (range 10°C to 20°C) with 70% humidity and a 25% chance of rain. Hokkaido summer — cool and pleasant compared to mainland Japan. Occasional fog from the Sea of Okhotsk.
Are crew and pacers allowed at Lake Saroma 100km Ultramarathon? +
No crew access is permitted. Pacers are not allowed.
What is the course record for Lake Saroma 100km Ultramarathon? +
The men's course record is 06:09:14 set by Nao Kazami in 2018. The women's course record is 06:33:11 set by Tomoe Abe in 2000.
What is the average finish time for Lake Saroma 100km Ultramarathon? +
The average finish time is 11:00:00. About 2,500 runners finish each year. The DNF rate is 12%.
Are you the organizer? Claim this race
Stay in the loop
New races, course records, and stories from the trail — monthly