The 23-year-old started the final 18 holes with a five-shot lead and plotted his way carefully round the Montgomerie Maxx Royal course to finish with a three-under-par 69 and a 24-under aggregate of 264.
Britain's Jamie Donaldson, helped by a hole-in-one at the par-three 16th, was two strokes adrift in second spot after a dazzling nine-under 63.
World number one Tiger Woods (67) never really threatened and had to be content with a share of third place on 268 with U.S. Open champion Justin Rose (65) in the penultimate event of the European season.
Dubuisson grinned like a Cheshire Cat at the presentation ceremony and was almost lost for words after picking up the first prize of 848,930 euros ($1.13 million), the biggest payday of his fledgling career.
"I wanted to cry there on the 18th green," he told Sky Sports television after being doused with champagne by a posse of his fellow French players.
"I don't really know what's happening right now. I was so busy concentrating on my game that it hasn't sunk in that I've won such a big event. I'm just so happy."
Dubuisson was a model of consistency early on, reeling off nine straight pars before picking up his first shot of the day at the 10th.
He remained in front until dropping his first shot of the round at the 14th, at the same time as Abu Dhabi Championship winner Donaldson produced a bolt from the blue at the 165-yard 16th, his tee shot pitching six feet short before rolling slowly into the cup.
No sooner was Dubuisson caught on 21-under by Donaldson that the Welshman's playing partner Rose made it a three-way tie for the lead by knocking in an 18-footer for a matching birdie.
The bearded Frenchman responded in the manner of a true champion at the 308-yard 15th, powering his tee shot to the fringe of the green before restoring his lead with a chip and a putt for birdie.
Dubuisson then added the icing on his victory cake by converting putts of 25 and 15 feet for birdies at the 17th and 18th.
"The start was a little bit difficult for me today," he said. "I wasn't playing too well and wasn't making any putts on the front nine.
"I was watching the leaderboard and seeing all the good players getting nearer to me. I spoke to my caddie and he just said, 'If we make one or two birdies at the end we'll be fine'.
(Reporting by Tony Jimenez, editing by Tony Goodson)
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