In his 255th European Tour event and after a career in which he has had to battle with a genetic spine problem, 36-year-old finally tasted victory in the Irish Open at Royal Portrush - and did it by four shots with five birdies in his last seven holes.
This was the first time since 1953 that the tournament had been played north of the border and what a success it was, with record crowds ever for a regular Tour event - over 112,000 for the four days.
Every one of them will hope it leads to the return of the Open Championship after even longer - Max Faulkner won that 61 years ago - and Donaldson will join them in that wish.
The former amateur star, who partnered Luke Donald and Paul Casey in the world team championship in 2000, has suffered from Pars disease, but careful management of it has finally enabled him to fulfil his dream.
His brilliant closing 66 was only one off the low round of the week and a 25-foot putt on the last enabled him to reach 18 under par.
"I'm buzzing," he said. "And I'm so happy to have won on this course - I don't think we have played a better one on the European Tour."
Reminded of his long wait to break through - it has contained 32 top 10 finishes - Donaldson added: "It's just been a case of keeping going. I knew that what I was doing was right.
"It feels a bit surreal to be honest. I don't think it will sink in till later."
The week also contained his first hole-in-one on the circuit and it began with him shooting 62 at Sunningdale to qualify for The Open at Royal Lytham in just over a fortnight.
Joint second were England's Anthony Wall, Spaniard Rafa Cabrera-Bello and Paraguay's Fabrizio Zanotti, but it was Swede Mikael Lundberg who threatened most to grab the title away from Donaldson.
From six back he covered the first 10 holes in a spectacular eight under and led by two. He could not keep it going, though, and bogeys at the 16th and 18th meant he eventually finished joint fifth.
With the local "Big Three" of Rory McIlroy, Graeme McDowell and Darren Clarke finishing 10th, 16th and 39th respectively the main Irish hope was 2007 winner Padraig Harrington.
He was only two behind when he teed off, but a disappointing 70 dropped him to joint seventh.
Donaldson, one in front of Wall overnight, chose not to look at leaderboards all day and it was only once he had reached the final tee that he asked caddie Mick Donaghy - new on the bag this week - for the position.
The news was good. He was two ahead and that became four when Wall, bunkered off his drive, bogeyed and Donaldson put the icing on the cake with his long birdie putt.
He had earlier had three in a row from the second, then came back with a bogey at the short 11th with three in the next four holes and after dropping a shot at the 16th - he was the one in sand there - he closed with two more.
Wall's bogey at the last was disappointing, but to be in a tie for second was remarkable given that he had gone out of bounds and taken a triple bogey eight at the second.
The Londoner, without a win since 2000, played the next 15 holes in six under to finish with a 69.
Zanotti and Dubai Desert Classic winner Cabrera-Bello both matched Donaldson's 66 and the Canary Islander's performance lifts him back into a qualifying position for the Ryder Cup with only two months of the race to go.
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McIlroy, who came in on the back of four missed cuts in his last five starts, was delighted with his ball-striking, but will hope to putt much better when he next plays at Royal Lytham.
"Tee to green it was a big improvement," said the world number two after his 67 today. "That's what I've been working on and maybe neglecting my short game.
"I've just got to get that sharp now and prepare for The Open - and I'd love to see that come here."
Clarke echoed that and was able to draw positives from the fact that he had finally made a halfway cut this season.
"It's been an absolutely brilliant week," said the Open champion, who still has this week's French Open to try to boost his confidence further.
"Obviously I would have liked to score a bit better than I did, but overall I think the event has been enjoyed not just by the professionals, but by the spectators and everybody involved."