London 100K
Four linked 25K sectors turn central London into a 100K urban ultra, with landmark-heavy navigation, indoor race headquarters and a 17-hour limit.
Quick facts
- Four 25K sectors return to the same central London headquarters.
- Mostly paved urban running with some trails and open-road crossings.
- Seventeen hours for the 100K, with checkpoints on every sector.
- The 50K and 25K challenges are separately entered sibling races.
Is registration open for the 2027 London 100K?
Registration for the 2027 London 100K is open.
About the London 100K
London 100K is an urban ultramarathon built around access rather than remote logistics. The 100K is the longest of four separately entered challenges and returns to a central indoor headquarters between sectors. Runners see the city in four directions while checkpoints and public transport keep crew access unusually simple for this distance.
Course
The route uses four 25K sectors heading east, north, south and west from central London. Pavement carries most of the distance, with some trail sections, open-road crossings and ordinary city navigation. Each sector returns to race headquarters, and checkpoints sit there and near the midpoint of every sector. The 100K limit is 17 hours.
Race-day weather
June in London is usually mild but changeable. A cool start can turn warm in exposed streets, while rain and wind remain plausible across a full day outside. Layers that pack down and reliable wet-weather protection suit the long urban schedule.
Past London 100K dates and results
| Year | Date | Status | Results |
|---|---|---|---|
| 2027 | Saturday, June 12, 2027 | Upcoming | — |
| 2025 | — | Completed | Open results |
London 100K FAQ
When is the London 100K?
The 2027 London 100K is on Saturday, June 12, 2027.
Is registration open for the 2027 London 100K?
Registration for the 2027 London 100K is open. View the official registration details at race-nation.co.uk.
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