At the end of a rainy day filled with the kind of crashes that are emblematic of this sport, Vaultier won his first Olympic medal in his third trip to the Games.
Olyunin finished first in his heat in the opening round, the quarterfinals and semifinals, but Vaultier jumped in front early in the six-man final and held on when Olyunin made a charge late in the race.
The bronze medal went to American Alex Deibold, who barely made it into the final round. Deibold and fellow-American Trevor Jacob both crashed as they reached the line in the semifinals and it took a look at the photo to determine who got to the line first.
Omar Visintin of Italy and Cameron Bolton of Australia were also eliminated as a result of crashes. Bolton's face was bloodied in his spill and Visintin had to be taken away on a stretcher.
American Nate Holland, a seven-time winner of this event in the X Games, stayed on his feet but was eliminated in the opening round when he finished fourth out of five. Only the top three in any heat advance to the next round.
Holland, running second at the time, landed poorly on one of his jumps and although he maintained his balance he lost all momentum and fell out of contention.
The event had been scheduled for Monday, but heavy fog postponed the competition 24 hours. Although the fog dissipated, heavy clouds rolled in and rain mixed with snow fell around the mountain venues at the Olympics.