Trail ultramarathon · South Korea
2–4 October 2026 · Jeju Island, South Korea
Jeju20K: Sat, 3 October 2026
A Korean island ultra around Jeju with volcanic terrain, Hallasan-area climbing, coastal humidity, and strong Asia-Pacific trail demand.
Entry · Jeju20K · 2026 edition
The organizer listed Jeju20K as full on 30 Sep 2026. A place can only come through the organizer's own transfer or waiting-list rules, if any.
From the organizer's page, checked 30 Sep 2026. TrailSplits does not know whether you have a place; the organizer is the final word.
TransJeju by UTMB is a trail ultramarathon scheduled for 2–4 October 2026 in Jeju Island, South Korea. TrailSplits currently includes 4 mapped courses for this event, with course maps, elevation profiles, weather context, and pacing tools for the uploaded GPX data.
How to get a place: First come, first served for the 2026 edition: registration opened 18 March 2026 (20K general from 20 March) and closes 31 July 2026. The 60K, 100K and 100M need a valid UTMB Index. Organizer's page, checked Wednesday 30 September 2026.
TrailSplits is a free, independent route & pacing companion — not the official race. Visit the official TransJeju by UTMB site →
The organizer lists Jeju20K at 20 km and +508 m for 2026; the course file mapped here (the organizer's 2026 file) measures 19.4 km. Small differences come from how each figure was measured; plans and pacing here use the mapped file. Organizer's race list, checked Wednesday 30 September 2026.
Finishing Jeju20K earns 1 Running Stone (20K category) toward the UTMB World Series Finals lottery. How Running Stones work.
Racing more than once next year? Add Jeju20K to a season and see whether your races work together.
Inspect the official course track on a topographic map, through its elevation profile, or in 3D.
› running direction two lines: out and back on the same path kilometres
Selected distance
Vert-focused blueprint with route-finder links into the Planner.
Other distances
Prepare and return
Keep this course, its training plan, calendar and future course updates together in your private My Races page. Saving does not publish your workouts, pace or progress.
Race route lab
Open the official course in Planner, then choose a nearby start point to build a shorter loop that matches the course demand. This course averages about 25.4 m climb per km.
Sat, 3 October 2026
Send to your watch
Get the official course as a clean GPX or a Garmin TCX course, with step-by-step instructions to load it onto a Garmin, COROS, Suunto, Wahoo, or Komoot — free, no account needed.
Compare your training
See how faithfully your rehearsal route matches the real race. The official course for Jeju20K loads as Route A — upload your training route to compare distance, elevation gain, estimated time, and how much of the course you actually cover.
Course analysis
See the Jeju20K course broken into its major climbs and descents in order — length, gain, average grade, and steepness — so you know where the crux is and how to pace and fuel it.
Race-week reminders
A free browser notification in the final week — the course crux, the weather window, and loading the GPX onto your watch. No app, no email, no account.
TransJeju by UTMB 2026 races run 2–4 October 2026 in Jeju Island, South Korea; the Jeju20K is on Sat, 3 October 2026. Check the official race site for registration deadlines and final details.
4 distances (20–148 km). The longest course is 148 km with about 5,000 m of vertical gain — a demanding mountain course.
The Jeju100M course has a 37-hour cut-off, an average of 15.0 min/km to finish in time. TrailSplits' cut-off pacer shows the buffer at each aid station.
Yes. TrailSplits gives you the course map, an interactive elevation profile, a 3D flyover and a downloadable GPX for every mapped distance — free and with no sign-up.
Each distance has a free, course-specific 16-week training plan built around its distance, vertical gain and cut-offs, plus a pace and cut-off calculator.
No. TrailSplits is a free, independent route and pacing companion. For registration and official rules, visit https://transjeju.utmb.world/.
Load the GPX directly into TrailSplits for surface analysis and terrain intel.