Reigning world champion Von Allmen hit speeds of 145km/h (90mph) to clock a winning time of 1min 51.61sec down the testing Stelvio course.

The 24-year-old Swiss racer broke the hearts of the home nation, finishing ahead of the Italian pair of Giovanni Franzoni, who was 0.20sec behind, and Dominik Paris (+0.50).

Pre-race favourite Marco Odermatt, Von Allmen's Swiss teammate, could only finish fourth.

"It feels like a movie," Von Allmen said.

"My secret is to enjoy skiing! I was really relaxed in the morning and tried to keep the good feelings... Skiing must be fun.

"We all skied because it was fun. It has to be in the foreground, be it skiing or any other profession, because you have to do it every day."

Franzoni, also 24, said the nerves had kicked in at the start.

"I saw the runs from the Swiss guys, they were getting better and better. I thought it would be hard to beat them, but I skied really well," he said.

"It's cool to be part of a new generation of alpine skiers, cool to be on podium."

Alexis Monney was the first of the Swiss quartet to tackle the Stelvio, immediately taking the lead off Austria's Daniel Hemetsberger.

Then came Odermatt, the in-form Swiss who is the runaway World Cup overall leader with three downhill victories to his name this season.

He snatched provisional top spot in beautiful, sunny conditions, but could only watch with bated breath as his understudy took to the start hut.

Von Allmen was fast out of the blocks and duly took the lead, soaring more than 50 metres off one jump to gasps from the large crowd packed into the tribune and around one side of the finish area.

It was a truly majestic display of skiing by the low-crouching Von Allmen, who has won two World Cup downhills this season.

His performance ensured he became the fifth Swiss men's Olympic downhill champion since 1948 after Beat Feuz, Didier Defago, Pirmin Zurbriggen and Bernhard Russi.

Austria's Vincent Kriechmayr, the 2021 double speed world champion, was hot on their heels, but failed to bother the leading Swiss trio.

- Italians in hot pursuit -

The Italians all had starting numbers in double digits, Franzoni the first of the 'tricolori' pack down.

He briefly took the lead at the third interval, leading to chants of "Giovanni" from the large number of Italian fans.

But the 24-year-old, winner of a super-G in Wengen and downhill in Kitzbuehel this season, lost that advantage in the bottom half of what is widely regarded as one of the toughest courses on the circuit.

Franzoni eventually streaked through in second place, just 0.20sec off Von Allmen, who was left clutching his face in relief in the leader's chair in the finish area.

Then came Paris, considered a real threat on the Stelvio course where he is a seven-time World Cup winner (six downhill, one super-G).

The 36-year-old delivered a slick run, but it was only good enough for third. It was a first Olympic medal for the Italian veteran in his fifth Winter Games.

"Getting the first medal in front of the home crowd, that's really special," said Paris.

Paris' efforts meant that Odermatt finished 0.20sec off the podium in his quest to add to the Olympic giant slalom gold he won in Beijing four years ago.

"It's a fourth place, it's not what I was hoping for," said Odermatt. "I had a good feeling actually, but it was just not fast enough.

"I felt very good, I had a good run and I don't know what I could change right now if I had to do it again."

Von Allmen's gold-medal showing set a fine precedent for the Swiss men's team that dominated last year's world championships in Saalbach, Austria.

The Swiss will look to confirm their fine form in Monday's Olympic team combined before tackling the super-G on Wednesday.