Final leaderboard (GB & Ire unless stated, par 71):
-15 G McDowell -12 R Davies -10 L Donald -9 R Rock, S Gallacher, E Molinari (Ita) -8 M Siem (Ger) -7 MA Jimenez (Spa) -5 N Fasth (Swe), R McEvoy, T Bjorn (Den)
By Peter Shuttleworth
BBC Sport at The Celtic Manor
Northern Ireland's Graeme McDowell celebrates his final round 63
Graeme McDowell enhanced his bid to return to the Celtic Manor in October as part of Europe's Ryder Cup team as he won a thrilling 2010 Wales Open.
The Northern Irishman, who made his Ryder Cup debut in 2008, shot a superb final-round 63 to card 15 under par and beat Wales' Rhys Davies by three shots.
Davies fired a stunning course record of 62 but McDowell showed composure and class to win his fifth tournament.
England's Luke Donald finished two shots further back on 10 under.
Scot Stephen Gallacher bogeyed the final two holes to spoil his round, finishing in a three-way tie for fourth with Robert Rock of England and Italy's Edoardo Molinari.
The £300,000 first prize is McDowell's first victory since his 2008 triumph at the Scottish Open and takes him to the verge of the qualification places to make Colin Montgomerie's team to take on the United States.
The 30-year-old is now up to 12th on the European Tour's Race to Dubai money list after almost doubling his season earnings with victory at the Celtic Manor.
"I think it's the best final round I've ever played to win a tournament," said McDowell, the 11th different winner in the Wales Open's 11-year history.
"The first 11 holes was dream golf and I am ecstatic. I feel like I'm in the form of my life right now and I really feel I have a big event in me.
"I honesty contemplated missing the cut on Friday as it was one over and I was two over. I thought I could be going home this week and it shows the fine line between success an failure.
"That has been coming for a while and I played phenomenal in the final 11 holes on Friday, I played lovely on Saturday and I came out and did the same on Sunday.
"I've been playing well for a while and I believed in myself and I couldn't have scripted those 11 holes I played out there today better."
Watching European captain Montgomerie would have been impressed as he saw a dramatic final round unfold on the course that will host the Ryder Cup from 1 October.
The final Celtic Manor leaderboard had a home nations feel with a Northern Irishman, a Welshman, two Englishmen and a Scot making up five of the top six places in front of a record 15,820 crowd in Newport.
McDowell - who once lived in south Wales - started four strokes adrift but began quickly with six birdies in his opening eight holes, starting by holing a 20-foot putt on the first to birdie the 465-yarder.
His faultless final round - including another 20-foot putt at the 16th to save par - ensured he completed the biggest final-round comeback since the £1.8m tournament started in 2000.
Home hope Davies celebrated his second successive second place to move tantalisingly close to the one million Euro barrier.
Bidding to be the first Welsh winner of the tournament, the 25-year-old started his final round steadily with three successive pars before an incredible eight holes where he picked up eight shots.
Davies, who won the Hassan II tournament in Morocco earlier this year, picked up six birdies and a superb eagle on the 439-yard par four eighth - sinking an eight-iron approach.
The Welshman saved par at the par-four 14th after dropping into the water, but the European Tour rookie recovered to eagle another par four as he took just two shots at the 377-yard 15th.
I had a really relaxed attitude and was going to accept anything that came my way
Davies suffered his first dropped shot of the afternoon at the par-four 16th but still lowered the Twenty Ten course record to 62.
That came just hours after Marc Warren had equalled the previous best - set on Saturday by fellow Scotsman Stephen Gallacher - as he fired 63 to end on four under.
Davies is renowned as an impeccable putter and he needed just 22 putts in his final round that secured his fifth top-three finish in an impressive rookie season.
His £200,000 runners-up cheque should move him to fifth in the top five of the European Tour's Race to Dubai money list and just outside the automatic Ryder Cup qualification places to face the Americans.
Davies joins Bradley Dredge, who was second behind South African Richard Sterne in 2007, as the closest Wales have had to a home winner.
"It was incredible," said Davies. "I had a really relaxed attitude and was going to accept anything that came my way and felt quite comfortable."
Two-time Ryder Cup winner Donald shot an excellent and unblemished final round of 65 to move up from joint 14th overnight to finish third - following on from second at the PGA Championship at Wentworth and his win at last week's Madrid Masters.
Overnight leader Marcel Siem put two balls in the water and ran up a quadruple-bogey seven at the 189-yard third, ending the German's challenge despite having led by three at the start of Sunday's play. Siem finished on eight-under.