TransJeju by UTMB
TransJeju by UTMB — 100M
Seogwipo (Jeju World Cup Stadium)
Race guide
Updated 19 July 2026
The TransJeju by UTMB 100M is a 148-kilometre circumnavigation of Jeju Island, South Korea, starting and finishing at the Jeju World Cup Stadium in Seogwipo. With 4,869 m of cumulative elevation gain and a high point of 1,919 m, this is a genuine mountain ultra routed across one of Asia's most dramatic volcanic landscapes — coastal trails, dense forest ridges, lava-rock terrain, and the volcanic peaks that define the island's interior. The race carries UTMB Series status and draws an international field, with a final cut-off of Day+2 at 10:00, giving runners roughly two full days to complete the course. That window sounds generous until the terrain and heat take their toll.
Course & Terrain Overview
Starting at 80 m above sea level at the Jeju World Cup Stadium, the course rises dramatically to a high point of 1,919 m before returning to the stadium finish at 81 m. The 148 km route threads through Jeju's distinct landscape layers: exposed coastal paths, forested volcanic slopes, and the rocky ridgelines that define the island's mountainous spine. Lava-rock underfoot is a constant feature — technically demanding, hard on quads and ankles, and punishing on tired feet in the back half. The terrain is never technical in an alpine sense, but the uneven volcanic rock demands consistent focus from start to finish, and the cumulative 4,869 m of climbing is distributed in a way that keeps the legs honest throughout rather than concentrating punishment in one or two obvious walls.
Decisive Climbs and Where the Race Is Won or Lost
The high point of 1,919 m is the pivotal moment of the course — reaching it and descending cleanly requires legs that have been managed carefully since the gun. The real danger on this course is the seductive ease of the early kilometres. Leaving Seogwipo and moving through the initial sections, the trails can feel welcoming and fast. Runners who respond to that feeling and push the pace early are making a deposit they cannot afford — the volcanic terrain and accumulated climbing will collect the debt in the second half with interest. The race is genuinely decided on the far side of the high point: those who arrive there with controlled legs and intact quads can run the descent and the remaining kilometres aggressively; those who pushed the early sections will be reduced to survival mode long before the finish stadium comes back into view.
How to Pace This Race
The proven approach here is a patient — even sociable — first half that functions as a deposit on a strong finish. Do not be spooked by feeling like you are going 'too easy' in the opening 60-70 km; that restraint is precisely what funds a devastating second half. The cutoff structure (Day+2, 10:00 finish) rewards runners who think in terms of two full days, not a single effort. Break the race mentally into segments rather than treating it as one continuous push: managing the psychological weight of 148 km is as important as managing the physical load. A useful reset strategy is chunking the back half into short horizons — two more checkpoints, two more ridges — rather than staring at the remaining distance as a monolithic block. Runners who adopt this mindset, staying calm and methodical through the second night, consistently outperform those who burn emotional and physical reserves trying to bank time in the first half.
Fueling & Hydration Strategy
With 148 km and up to 48 hours on course, fueling discipline is non-negotiable. The combination of volcanic terrain, potential heat, and sustained climbing means caloric expenditure is high and consistent — this is not a course where you can skip feeds and make up ground later. Eat early and eat often, even when appetite has not yet arrived, because on a two-day effort the hunger signal lags behind the actual deficit significantly. Heat is a factor on Jeju, particularly through exposed coastal and lower-elevation sections during daylight hours. Build planned cooling resets into your race-day schedule rather than reacting to heat stress as it arrives — structured breaks to cool down, rehydrate, and reset mentally transform heat from a threat into a managed variable. Carry sufficient fluid capacity between checkpoints and treat electrolyte management as seriously as calorie intake given the humidity typical of Jeju's climate.
Conditions to Expect
Jeju Island's weather is shaped by its maritime and volcanic geography, which means runners should prepare for humidity, wind exposure on the higher ridgelines, and the possibility of significant temperature swings between the sun-baked lower coastal sections and the cooler, windier high point at 1,919 m. Night sections — and this race involves at least one full night on course, often two — bring a sharp temperature drop, so layering systems that can be easily managed on the move are essential. The lava-rock trail surface is abrasive and unforgiving in wet conditions, so trail shoes with genuine grip and protection underfoot are a priority over pure speed shoes. The two-day cutoff window means runners must also be prepared for sleep pressure and the cognitive load that comes with racing through a second night — mental preparation for the dark kilometres is as important as any physical training block.
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Checkpoints & cut-offs
✓ Course data verified against the official source (2026-07-05) · official source
0 km · 79 m · Fri 21:00
7.2 km · 414 m · Fri 22:40
20.3 km · 1225 m · Sat 02:40
28.7 km · 974 m · Sat 05:10
40.8 km · 578 m · Sat 07:10
58.6 km · 755 m · Sat 12:40
66.5 km · 448 m · Sat 14:40
88.4 km · 275 m · Sat 18:40
105.2 km · 253 m · Sat 22:40
115.1 km · 445 m · Sun 01:00
126.5 km · 494 m · Sun 04:00
136 km · 414 m · Sun 07:00
147.6 km · 81 m · Sun 10:00
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