The 40-year-old was part of a group of freeriders that was descending the 3,000 metre peak Gemsstock in Uri, Switzerland when a patch of snow broke off.
Ski Chrono reported that Bruno Putelli, a guide and rescuer with the CRS des Alpes in Albertville, also died.
Other members of the group managed to escape and raise the alarm.
"The tragic death of Julie, world snowboard champion and Olympian, leaves the French Olympic team in mourning for one of its own," the French Olympic committee wrote on Twitter.
Toutes les pensées de l'équipe de France Olympique et du CNOSF vont à la famille de Julie Pomagalski, à ses proches, à @FedFranceSki. La disparition tragique de Julie, championne du monde de snowboard et Olympienne, laisse l'équipe de France OLY en deuil de l'une des siennes. pic.twitter.com/BtXqH398io
— France Olympique (@FranceOlympique) March 23, 2021
Pomagalski, who was born near Grenoble, was still in her teens when was crowned world snowboard cross champion in 1999 at Berchtesgaden in Germany. She went on to win the World Cup in 2004.
Juggling several disciplines - parallel slalom, parallel giant and boardercross - she took part in the 2002 Salt Lake City Olympics and the 2006 Turin Olympics.
After stepping away from international competitions, she ran her own ski school and sports shop in the resort of Méribel in eastern France.
She was also the granddaughter of Jean Pomagalski, founder of the world-famous ski-lift manufacturing company, Poma.
