The 35-year-old from the Czech Republic was taking part in a warm-up event ahead of the Ultra-Trail du Mont-Blanc, a famed endurance event that takes place every year around western Europe’s highest peak.
The man fell during the night after setting off with more than 1,000 other runners from the Italian ski resort of Courmayeur on Tuesday afternoon along the 145-kilometre course of the TDS race to Chamonix in France.
Emergency services were alerted after midnight on Wednesday and flew in a helicopter to the scene of the accident in the Bourg-Saint-Maurice district, but they were unable to revive him, local police commander Patrice Ribes told AFP.
Organisers of the Ultra-Trail du Mont-Blanc, which takes places on Friday, said it was the first death in one of their events since their start in 2003.
Elsewhere in the French Alps on Wednesday, a 60-year-old climber died in the Isère region after suffering a fall of 30 metres.