Sylvain Saudan, who was widely known as the “skier of the impossible” for his audacious and potentially life-ending descents down some of the steepest, most inaccessible slopes in the world, died on July 14 at his home in Les Houches, France. He was 87.

His longtime partner, Marie-José Valençot, said the cause was a heart attack.

That Mr. Saudan lived into his ninth decade puzzled many people — including Mr. Saudan himself.

Beginning in 1967, when he plunged down the Spencer Couloir on the Aiguille de Blaitière mountain in France — a 55-degree slope roughly equivalent, on skis, to a free fall — Mr. Saudan spent his life defying gravity, avalanches and obituary writers.

“One mistake, you die,” Mr. Saudan once said. “You fall, you become a prisoner of the mountain — forever.”

In careening down alarmingly steep, previously untraversed slopes in the Alps, the Himalayas and elsewhere, Mr. Saudan helped create an entirely new sport: extreme skiing, now known as steep skiing. Its enthusiasts travel to remote peaks, often by helicopter, and try to have positive thoughts when looking down.

“Death? It is there for everyone, but fortunately we forget about it,” Mr. Saudan told the Swiss newspaper 24 Heures in 2016. “If you only look at the negative side, you don’t move forward.”