A 180km volcanic crossing of Réunion Island — the world's most brutal diagonal
The 'Madmen's Diagonal' is one of the world's most iconic ultramarathons — a 180-kilometer crossing of Réunion Island from the waterfront of Saint-Pierre in the south to the Stade de la Redoute in Saint-Denis in the north, accumulating over 10,000 meters of elevation gain through UNESCO World Heritage terrain. Starting at 10 PM under headlamps, runners traverse three dramatic volcanic cirques, dense tropical rainforest, and exposed ridgelines. The 2026 route runs through the Salazie cirque rather than Cilaos, making this the longest edition in race history at 180km. Alternating between tropical heat at the coast and alpine cold above 2,500 meters, the race demands navigation through the island's full ecological range over up to 66 hours — earning those who finish the title of 'Fou' (Madman).
Recommended for seasoned ultrarunners
Saint-Pierre, ReunionOctober 15, 2026
In 2026, 3,429 candidates competed for approximately 1,550 lottery spots (out of 3,000 total places). Remaining spots distributed via packages and partner allocations. Demand far exceeds supply.
Must meet custom qualifier requirements within the qualification window
Must have earned at least 75 ITRA points by completing a qualifying trail race of 40km+ with a minimum 2,000m positive elevation gain
| Location | km | Elevation |
|---|---|---|
Start Start | 0.0 | 19 m |
Finish Finish | 180.7 | 66 m |
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October weather on Réunion is highly variable and changes rapidly with altitude. Coastal sections around Saint-Pierre can be hot and humid, with temperatures reaching 28–32°C / 82–90°F during daylight hours. As the course climbs into the cirques and toward Piton des Neiges, temperatures drop sharply — often below 10°C / 50°F above 2,000 meters, with wind chill adding further challenge during overnight hours. Tropical thunderstorms are a constant possibility in October, bringing sudden heavy rain and lightning on exposed ridgelines. Runners experience the island's full climate spectrum — tropical coast to misty rainforest to alpine — within a single race.
Course approaches 3,000m elevation near Piton des Neiges; alpine cold and wind chill can be severe above 2,000m
Rapid microclimate transitions between tropical coast (28°C+) and alpine terrain (near freezing) within hours of running
October tropical thunderstorms are common; exposed ridgelines above treeline can be dangerous during storms
Coastal and lower-elevation sections are hot and humid in October, especially during daylight hours
No required gear specified
No recommended gear specified
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