Despite going into the final day’s 12 singles matches 10-6 down to the USA, Westwood and Europe clinched a famous 14½-13½ victory at Medinah Country Club, Chicago.
The Worksop golfer beat Matt Kuchar 3&2 to seal a vital point on Sunday, as José Maria Olazábal’s men silenced the US fans and turned momentum in their favour.
Europe came out all guns blazing on the final day, winning the first five singles matches.
Dustin Johnson, followed by his namesake Zach, stemmed the tide and put the USA back in the lead at 12-11.
Sergio Garcia’s come-from-behind victory over Jim Furyk levelled things once more, before Jason Dufner beat Peter Hanson, but that was the last match the home side were to win.
Westwood held his nerve to hole out from a foot on the 16th, and Germany’s Martin Kaymer also showed a remarkably cool head to sink the putt that retained the trophy, beating Steve Stricker at the last.
With wild celebrations starting, Francesco Molinari was handed a half on the 18th green by Tiger Woods, and Europe were outright winners.
For Westwood it was the best possible finish to a tough Ryder Cup – his eighth.
He began the weekend, alongside Molinari, with defeat to Dufner and Zach Johnson in the Foursomes.
But an incredible performance from his Fourball partner Nicolas Colsaerts brought victory over Woods and Stricker.
A humiliating 7&6 defeat in Saturday’s Foursomes followed, Westwood and Luke Donald enduring their worst ever loss in the competition.
After sitting out a session, Westwood came back with a bang on Sunday and holed putts like his life depended on it in the final stages against Kuchar.
Speaking after his round the 39-year-old admitted he was shaking with nerves on the 16th as he attempted to win the match, and his 21st career Ryder Cup point.
“I was nervous over that one-footer, I tell you what, that’s pressure,” he said.
“I don’t blame him for not giving it to me, I was shaking like a leaf. I make no apologies for this, it’s the ultimate pressure in golf.”
“You’re playing for a lot of pride and it’s just nice to roll it in and win.”
Westwood went on to say that a European victory would be the ‘greatest comeback in the Ryder Cup, ever’ and then danced with joy alongside his team-mates as the comeback was completed.