Just two hours after a tearful Mellisa Hollingsworth apologised for "letting my country down" after blowing her chance of gold in the women's race, Montgomery produced a perfect fourth run then watched Martins Dukurs self-destruct.
Latvian Dukurs held a 0.18 advantage going into the final run but cracked on the final corner just when his country's first Winter Olympics gold looked to be in his grasp.
"That was what I was hoping for, that was what I set out to do at the top of the track before that fourth run," Montgomery, who won by seven hundedths of a second, less time than a human being takes to blink, said.
"I was happy with that performance. I said to myself 'that's gotta be close to good enough. That's got to be close.' I was biting my nails for sure."
Dukurs and Montgomery had been locked in battle since Thursday's first slide, both of them smashing course records, as the rest of the field scrapped amongst themselves for bronze.
Montgomery was 0.28 seconds behind after Thursday's first run but chipped away at the deficit before launching his attack with a faultless descent in heat four.
It all proved too much for Dukurs.
"I started to realise that there was a possibility that I could win this race when he went late into nine and from that point those minus numbers got lower and lower until all of a sudden he was in the plus range. Then I lost my mind!"
Dukurs tried to hide his disappointment at the finish.
"I'm a little bit disappointed with the last run. But not disappointed about the result," said track rat from the Latvian sliding stronghold of Sigulda.
"I came here thinking the top three will be great. So I did that and I'm happy. Jon's been consistent and in training I saw that he's smashing it down."
Alexander Tretyakov of Russia took the bronze. British slider Kristan Bromley was sixth.
Bromley went into the third run in fifth, just five-hundredths of a second off the medal places but he dropped down a place with a 52.70 on his third run. He followed that up with 52.80 on run four – the seventh fastest time of the run – but that wasn’t enough to put him on the podium.
Bromley’s final combined time of three minutes 31.30 seconds for the four runs put him 1.57 seconds off the winning time of Montgomery.
Bromley said: "I did my best, but I'm really disappointed I couldn't make the medals this time.
"I was really pleased with my last run, but I would like to have my third run over again. This is the pinnacle of everyone's career and we all want to win, but obviously we can't all do that."
Bromley, who is based in Sheffield, said it is too soon to think about his future in the sport in which he has already captured the World Championships, the World Cup crown and the European Championships.
"I’ve had an amazing career and some amazing experiences over the last 15 years. I can look back on that and be really proud.
"We do these adrenaline sports because we get a buzz from it and because it’s a challenge. That’s what we’re all up for. History has proven there’s another four years in me if I want it. I will see where I go in the summer."
The other Brit Adam Pengilly said he had been hampered with a knee injury during his Vancouver 2010 campaign which ended in 18th place.
The Bath-based slider, competing at his second Olympic Winter Games, said: "It's been a tough and disappointing week for me. I started to improve, but unfortunately it was too little too late."
One of Canada's other medal hopes Michael Douglas was disqualified before the third heat after being three minutes late taking his sledge for pre-race inspection.
Place of birth: Russell, Canada
Residence: Calgary, Canada
No previous Olympic results:
Silver medallist, 2008 World Championships, Individual
Runner-up, 2007/08 World Cup, Individual
Montgomery started the skeleton in 2002 after attending a talent identification camp. He is an athlete ambassador for the 'Right to Play' organisation.
The 30-year-old, who works in sales, is coached by Will Schneider and 2006 Winter Olympics skeleton gold medallist Duff Gibson of Canada.