American Seth Wescott took gold by less than a board length from Radoslav Zidek in a dramatic snowboard cross final in Bardonecchia on Thursday.
Wescott's aggression saw him through in a thrilling final
Wescott, 29, rode in the Slovakian's slipstream for much of the race before forcing his way past to become the first Olympic champion of the event.
France's Paul-Henri Delerue recovered from an early collision with Spain's Jordi Font to capture the bronze.
World Cup champion Jasey Jay Anderson was disqualified in the semi-finals.
Wescott, ranked fifth in the current World Cup snowboard cross season, has bounced back from two serious knee injuries.
He tore his left knee ligament in 2004 and damaged the right one three years earlier.
The American was joined in the final by an unlikely trio, after several favourites went out early.
Delerue is ranked ninth in the World Cup, while 24-year-old Zidek is rated 21st and Font, 30, is 98th in the overall rankings.
Canadian Anderson, who has been overall snowboard World Cup champion for four of the past five years, was ruled to have pushed Font as they approached a jump.
Both men went down but Anderson recovered to finish second before race officials ruled him out.
Delerue's older brother Xavier, a three-time World Cup snowboard cross champion, has been nursing an ankle injury and went out in the first round.
American Nate Holland, the World Cup co-leader with Xavier Delerue, crashed out in the quarter-finals after losing control on a jump.