Marathon des Sables (Morocco)

Marathon des Sables covers 250 kilometers across the Sahara Desert over six days, making it 35% longer than Comrades Marathon (#7) despite having a slower average pace of 15 minutes per kilometer. Participants carry all food and gear, enduring temperatures exceeding 50°C, which pushes DNF rates above 30%—double that of UTMB (#5) and eight times higher than Tokyo Marathon (#6). Its self-sufficiency rule demands 14,000 daily calories, yet finishers lose an average of 4.5 kilograms. As the 'toughest footrace on Earth,' it outperforms every other event on this list in extreme mental fortitude, with only 25% of applicants securing a spot due to demand.