The 2010 US Open winner finished the tournament with a nine-under-par total of 275 as an initially tense final round eventually became a one man show with McDowell cantering home to pick up a winner's cheque of €500 000.
His closest rival, Richard Sterne of South Africa, held the lead after nine holes before collapsing down the stretch and finishing with three bogeys in six holes while McDowell's rock solid game of just four bogeys throughout the tournament was the cornerstone of his second win of the year.
Sterne settled for second on five-under-par 279.
Englishman Graeme Storm and Spaniard Eduardo De La Riva were paired together for the final round and both men fired two-under-par 69s to claim a share of third spot on four under.
"I've always felt that this golf course
is one I can get around well.
"And coming into this week has been a bit strange for me, too many missed cuts and a little bit inconsistent," said McDowell.
"I felt my confidence coming back and hit the ball
beautifully Thursday, Friday, Saturday.
"And today I was very realistic about my chances.
"Myself and Richard (Sterne) kind of dragged
each other along there.
"He played really, really well and I knew it wasn't going to be an easy day.
"The way he was playing kind of inspired me to play better and it was a really good battle with him.
turning point was probably 15 and 16.
"Fifteen was an average putt that I
thought missed and it went in and sixteen I still don't know how it
"It was a right to left putt but I think the crowd sucked it in.
"I'm a very proud French Open winner."
Sterne led by one shot after nine see-saw holes before McDowell birdied the 10th to draw level and looked on as the South African drove his tee shot on 11 into the deep rough.
With no clear sight of the green, Sterne did well to get within 40 feet of the pin before getting down in two for his first bogey of the afternoon, putting McDowell back in the driving seat on eight under.
The 31-year-old from Pretoria looked certain to lose more ground at 13 when he sliced his second shot into the water but a fine approach shot and a 25-footer to save par kept him one back.
McDowell, who was looking for his sixth win in eight stroke play tournaments, and Sterne then headed towards what most players have described as the toughest four finishing holes on the European Tour.
Both players parred 15 before the treacherous par three 16th produced another swing in fortune for McDowell.
His tee shot missed the green before a lucky bounce left his ball in a position from where he was able to two putt for par.
meanwhile, showed the pressure was taking it's toll when he missed a 10-foot putt for par and his second bogey in five holes handed McDowell a
two-shot lead with two holes to play.
He never looked back.
McDowell's win follows his triumph earlier this year at the Volvo World Match Play Championship and puts him in second place in The Race to Dubai on €1 530 715, just €27 185 behind US Open champion Justin Rose.
Leading scores after the fourth and final round in the French Open at Le Golf National outside Versailles (GBR & IRL unless stated, par 71):
275 - Graeme McDowell 69-69-70-67
279 - Richard Sterne (RSA) 68-69-71-71
280 - Eduardo De La Riva (ESP) 72-67-72-69, Graeme Storm 70-68-73-69
281 - Simon Dyson 70-68-72-71
282 - Jamie Donaldson 70-70-71-71, Richard Green (AUS) 69-70-70-73
283 - Gareth Maybin 71-73-71-68, Stephen Gallacher 68-70-75-70, Thomas Bjorn (DEN) 68-69-74-72, Soren Kjeldsen (DEN) 69-68-73-73, David Howell 69-71-69-74
284 - Gareth Shaw 72-69-74-69, Martin Kaymer (GER) 68-76-69-71, Hennie Otto (RSA) 71-71-69-73, Marc Warren 69-72-70-73, Bernd Wiesberger (AUT) 70-71-68-75
285 - Victor Dubuisson (FRA) 68-75-76-66, Damien McGrane 70-72-74-69, Seve Benson 71-72-73-69, Felipe Aguilar (CHI) 68-72-74-71, Simon Khan 71-73-68-73, Francesco Molinari (ITA) 71-74-67-73, Jorge Campillo (ESP) 74-69-68-74
286 - Kristoffer Broberg (SWE) 72-69-73-72, Matteo Manassero (ITA) 73-69-73-71, Ian Poulter 73-71-69-73, Lee Slattery 71-70-70-75
287 - Thomas Pieters (GER) 70-72-75-70, Romain Wattel (FRA) 67-75-74-71, Scott Henry 73-68-74-72, Rafa Cabrera-Bello (ESP) 70-72-72-73, Robert-Jan Derksen (NED) 72-70-73-72