Sochi 2014 Olympic champion Marielle Thompson edged out Fanny Smith in a thrilling ski cross final at the World Championships in Solitude, Utah.
Thompson and Smith were quickest in timed qualification before making their way through three rounds to reach the four-woman big final.
France's Francois Place was the surprise men's winner beating PyeongChang gold medallist Brady Leman.
The return of Thompson
Sochi 2014 champ Thompson was favourite for gold after posting the fastest time in qualification and winning all three of her heats to reach the final.
But PyeongChang bronze medallist Smith jumped out into the lead in the medal showdown, breezing through the first three-quarters of the contest.
Thompson was down in third but muscled her way past Alizee Baron of France before going round the outside of 2013 world champion Smith on the penultimate corner.
And victory secured the Canadian a full set of major titles in her career.
"Going into the second-to-last corner I thought maybe I could generate some speed on the outside, and thankfully it worked out for me,” said Thompson who added the world crown to her Olympic title and the World Cup crystal globe.
Thompson was ecstatic after missing all of the 2017/18 World Cup season with a serious knee injury.
Just four months after tearing her anterior cruciate knee ligament, she went to PyeongChang to defend her Olympic title and topped the timesheets in qualification.
But Thompson crashed out just 100 metres into her first heat.
The 26-year-old returned to World Cup action this season, scoring four podium finishes without making the top step.
"Coming back this season I feel like I’ve been building my skiing back up at every race. So to come here to the biggest stage of the season and come out on top, I’m overjoyed!"
Baron finished third with Sanna Luedi of Switzerland was fourth.
World Cup leader Smith later rued allowing Thompson past which cost her a second world title six years after her first.
Place pips Olympic champ
Former alpine skier Francois Place sprung a surprise to take the men's title in just his third season in ski cross.
The 29-year-old had previously underachieved in World Cup slaloms and giant slaloms, making the second run just once in 40 races.
His finest moment came back in 2010 when he beat the likes of Mathieu Faivre and three-time Olympic medallist Alexis Pinturault to take the French Super Combined title.
Place made the switch to ski cross at the start of 2017 and won a shock bronze at the World Championships in Sierra Nevada, Spain.
In World Cup competition, he has been a regular top-10 finisher without ever reaching the podium.
The Frenchman was second in qualification in Solitude and moved through the bracket to the final.
He overcame a tricky early landing to move into the lead from Olympic champion Brady Leman, Kevin Drury and Alex Fiva of Switzerland.
And he held off Leman to take gold and bring his World Championship medal tally to two.
"It was an incredible race today. It was a little tough this morning with the weather and the wind, but in the end, it was a great day," Place offered.
"To be the champ, it’s cool."
Canadian team-mates Leman and Drury took second and third respectively with Leman delighted at his first World Championship medal.
He said, "To win the Olympics in Korea after being fourth in Sochi was incredible, and I’ve been really close at the World Championships before with a fifth and seventh. So to end up on the podium here is incredible."