The 38-year-old rookie conjured the shot of his life at the 15th hole, hitting a stunning wedged approach to the green to complete a 4&3 singles win over 2011 US PGA champion Keegan Bradley.
Donaldson was quickly engulfed by captain Paul McGinley, team-mates, caddies, friends and family as he celebrated his best moment as a professional.
“This week has been amazing,” said the blond Welshman. “The lads have got on so well, it’s been a great craic.
“It’s hard to describe how good the Ryder Cup is. There’s nothing else quite like it in golf – it’s just a total one-off.
“It’s just a huge, huge thing and it’s just been amazing to be a part of it,” he added.
Donaldson was always regarded as a journeyman player on the European Tour until he suddenly elevated his status by eclipsing the likes of Tiger Woods, Rory McIlroy and Justin Rose to win the 2013 Abu Dhabi Championship.
Since then his game has been transformed and he now features regularly on the leaderboards of the biggest tournaments around the world.
“I was four up with four holes to play there against Keegan and hit a really good tee shot,” said Donaldson.
“It was a perfect yardage and I played the wedge shot of my life to close the game out. I can’t really put words to it, it’s unbelievable.
“I knew it was all getting tight there at the end… I was just trying to not spend too much time looking at the scoreboard and just concentrate on my match.”
Donaldson refused to listen when a doctor told him to quit golf ten years ago.
He had such a chronic back condition in 2004 that one specialist suggested retirement, but he was given the go-ahead to continue after seeking a second opinion.
“The first doctor I went to see said, ‘don’t play’ so I went to see someone else,” said Donaldson. “That wasn’t what I wanted to hear.
“As soon as someone says that you just go and see someone else. The second guy I saw said I needed to do a load of core stability exercises… so I did a lot of gym work for a year.
“Now I don’t do that much gym work any more… to be honest I actually do none,” added Donaldson. “I do more physio stuff these days and I get massages before and after I play.
“But without doing the work I initially did nine years ago I wouldn’t have carried on playing. The back was really bad then.”