The American skier's boyfriend Connor Watkins went down on one knee in the snow at the finish area to make the proposal and present the sapphire and gold ring.
"I had told him that I always dreamed of getting proposed to at the Olympics, so I had an inkling," Johnson, who won her gold on Sunday, told reporters.
Watkins, who described himself as a poet working in the construction industry, said he had been planning for about a year and had needed a little help from the U.S. ski team and governing FIS to make it happen.
With Johnson smacking into a gate and then careering into the catch fencing, damaging her helmet, popping the question took on secondary importance.
"I was hoping she was OK, first and foremost," said Watkins, standing alongside Johnson and wearing a hat knitted by his partner.
"There was a plan B, just in case there needed to be, because you never know how the day is going to work out. Sometimes the mountains can be unforgiving," added the Georgia native who said he knew little about ski racing when the couple met.
The super-G was Johnson's last race at the Games.
"His words were so beautiful and just, like, I echoed so much of what he said. So I was just crying and thinking about how much I love him," she said.
"At my first Games, there was talk that one of my teammates was going to get engaged at the Olympics and it kind of just stuck in my mind. I feel like it just felt fitting to combine two of my loves and it's a special place.
"There's a lot of mystique around it. And you also get free photography."