The Diagonale des Fous: La Grand Raid de La Réunion’s Legendary Ultra

• Location: Réunion Island, France / Africa
• Distance: ~105 miles (170 km), up to 112 (180 km) starting with the 2026 edition 
• Elevation gain: ~34,449 feet (10,500 m)
• Event type: Point-to-point mountain ultramarathon 
• Part of / race series: Grand Raid de La Réunion 
• Date: Mid-October
• Participants: 3,000 maximum

What is the Diagonale des Fous?

The Diagonale des Fous is the flagship race of the Grand Raid de La Réunion, a multi-distance trail event on the French island of Réunion. The Diagonale des Fous route crosses the island south to north from Saint-Pierre to Saint-Denis, tackling terrain shaped by the active volcano Piton de la Fournaise, and the slopes of Piton des Neiges, the island's highest peak at 10,069 feet. Covering approximately 105 miles and 34,449 feet of total elevation gain within a 66-hour time limit, Réunion’s Diagonale des Fous is one of the most demanding ultramarathons on the international trail calendar. ultra

A cultural phenomenon on Réunion Island

The Diagonale des Fous on Réunion is something of a public holiday, with volunteers getting time off work to staff aid stations and residents lining the route to watch the spectacle. In fact, “La Diagonale des Fous” literally translates to “The Madmen’s Diagonal,” a reference to the disorientation and sleep deprivation competitors experience. Despite its difficulty level, Salomon athletes François D'Haene and Courtney Dauwalter have both left their mark on the race, with D’Haene winning four times from 2013-2018 and Dauwalter taking first for women and fourth overall more recently in 2022.

The five races of the Grand Raid

The Grand Raid de La Réunion offers several distances and events for participants to choose from.

Diagonale des Fous

The Diagonale des Fous distance charts a diagonal route north from Saint-Pierre to Saint-Denis, covering 105 miles, a similar length to the Ultra Tour Monte Rosa. Registration for the Diagonale des Fous requires two qualifying races.

Trail de Bourbon

Starting in Cilaos a day after the Diagonale, the Trail de Bourbon covers 66 miles, crossing three volcanic cirques, Cilaos, Salazie, and Mafate, in the process. With a similar profile to the UTMB® CCC®, the Trail de Bourbon only requires one qualifying race, making it a popular proving ground for runners preparing to attempt the full Diagonale des Fous.

The Mascareignes Trail

The Mascareignes is a 46-mile route (similar in length to France’s Grand Trail des Templiers) that departs from Hell-Bourg before descending the Cirque de Mafate's Scout trail and heading back toward the coast and finish line at La Redoute Stadium. Qualification requirements include a prior trail race but are less stringent than for the flagship race or Trail de Bourbon.

The Métis Trail

The Métis Trail is the Grand Raid de La Réunion’s shortest solo offering at 32 miles, with stretches along Réunion’s northwest coast from its start in Saint-Paul to the finish in Saint-Denis. With no qualification requirement, this newest addition to the Grand Raid could be an approachable entrypoint for newer trail runners.

The Zembrocal Trail

The Zembrocal Trail is a relay that stretches 99 miles in total from Saint-Joseph to Saint-Denis across four legs. It’s open to teams of up to four, and there is no qualification requirement.

Running the Grand Raid: gear

Due to the race’s demanding nature, proper trail running gear is non-negotiable. The Grand Raid requires runners to bring certain mandatory trail running equipment for protection and to stay hydrated on the trail, including:

• A headlamp or flashlight with spare batteries
• A reliable running backpack
• A water reservoir that can hold at least 1.5 liters
• A waterproof jacket
• A survival blanket

Recommended gear also includes a change of trail running clothing.

The volcanic surface through Mafate alternates between packed clay, loose scoria, and root-covered singletrack, so trail running shoes with deep, multi-directional lugs provide the best traction on steep or wet climbs and descents.

Browse women’s trail running shoes

Browse men’s trail running shoes

Temperatures swing from tropical heat near the coast to biting windchill above 7,000 feet, so both sun protection and a packable insulating layer are vital for comfort while running in the heat and/or wind.

Diagonale des Fous 2026 dates

The 34th Grand Raid de La Réunion runs October 15th-18th, 2026, with the Diagonale des Fous starting on the first day. The new Diagonale des Fous distance for 2026 is the longest edition on record at 112 miles or 180 km. Each year, up to 3,000 participants are drawn for the Diagonale des Fous via a lottery system, with certain quotas in place based on nationality.

Your Diagonale des Fous questions answered

How hard is the Diagonale des Fous?

The distance and elevation gain of the Diagonale des Fous, along with tropical heat, technical descents, and sleep deprivation, make this an epic challenge worthy of its “Madmen’s Diagonal” nickname. The number of starters who don’t finish the race usually hovers around 25%. For the best chance of a successful race, be ready to train for an ultra-marathon in the mountains over several months. Focus on dedicated preparation for high-altitude running and incorporate long runs to build endurance and practice managing effort on the trail.

What is the Grand Raid de La Réunion?

The Grand Raid de La Réunion is the umbrella event that includes the Diagonale des Fous alongside several shorter courses. All Grand Raid races finish at La Redoute stadium in Saint-Denis and share aid stations, gear checks, and volunteer support, bringing the whole trail running community together in Réunion during the three days of the Grand Raid.

The Diagonale des Fous: race the entire island

The Diagonale des Fous stands apart from other high-profile ultras for its tropical setting. It winds around volcanic cirques (with over 33,000 feet of climbing along the way) across a small island in the Indian Ocean that stretches only 50 miles from north to south. The island’s tiny size contrasts with the massive reputation the Grand Raid de La Réunion has earned in the trail running imagination.

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