Molinari, who finished 19-under par for the tournament, won for the second time in his career.
SHANGHAI (AP) -- The experience of losing to one No. 1 player in the world helped Francesco Molinari beat another.
When last seen on a world stage, Molinari was helpless against Tiger Woods in Ryder Cup singles, when the former world No. 1 steamrolled the Italian for an easy victory at Celtic Manor.
One month later at the HSBC Champions, Molinari turned in a world-class performance against the new No. 1.
In an exquisite duel with Lee Westwood that came down to the last putt, Molinari played bogey-free Sunday at Sheshan International for a 5-under 67, giving him a one-shot victory and a World Golf Championship title.
"It's been four fantastic days, and especially the last two playing head-to-head with Lee was really tough," Molinari said. "I think the experience of playing with Tiger in the Ryder Cup definitely helped me in the last couple of days, because when you are playing against No. 1 in the world, it is not easy to always stick to the game plan and do your game."
Woods was 7-under over the last seven holes in that Ryder Cup match against Molinari. He wasn't even close to that level at the HSBC Champions, where even a 68 on the final day still put him 13 shots behind in a tie for sixth.
He ended his PGA Tour season without a win for the first time in his career.
"That's just the way it goes," Woods said. "It's not like I didn't try. It just didn't happen this year. But I'm pleased with the progress I've made of late. Things are building and heading in the right direction, which is good."
Richie Ramsay of Scotland closed with a 71 and tied for third with Luke Donald of England, who faltered to a 73. For Ramsay, it was enough to secure a spot in the Race to Dubai finale at the end of the month.
Rory McIlroy of Northern Ireland had a 67 for a European sweep of the top five spots.
But this was Molinari's show. No one had a lower score in three of the four rounds, and he finished at 19-under 269.
It spoiled the debut of Westwood atop the world ranking, yet the 37-year-old Englishman could find little to regret except for a few bad breaks down the stretch and one poor flop shot at the worst time.
After making a 10-foot par on the 15th to stay one shot behind, Westwood his 3-wood on the 288-yard 16th and thought he was in perfect shape until his tee shot hit the back of a bunker and bounced forward, leaving him in an awkward spot with a pot bunker between him and the flag. His flop shot was fat and didn't clear the bunker, while Molinari hit lob wedge to 4 feet for birdie and a two-shot lead.
Still two shots behind playing the par-5 18th -- this after making a 15-foot par save -- Westwood hit 5-iron to the green and turned in disbelief when the ball crawled up a slope and didn't come back down toward the pin.
Instead, he had a 25-foot eagle putt to force a playoff, but the ball stayed left of the hole.
"I expected it to be running down, like 3 or 4 feet," Westwood said. "Just needed the breaks to win, and it didn't happen."
Even so, he put up a fight that was worthy of his ranking.
Westwood, coping with a calf injury all summer, was playing only his second stroke-play tournament in three months. He still managed to play without a bogey on the weekend -- he went the last 43 holes without dropping a shot -- and his 67 in the final round put him at 18-under 270. It was good enough to beat the rest of the field by nine shots.
The golf was at such a high level that neither player in the final group made a bogey, and Molinari figured he was going to have to make birdie on just about every hole to stay in front.
He only played it safe at the end, knowing Westwood would need an eagle to beat him. From the top tier of the 18th green, Molinari hit a beautiful lag, which he tapped in for par. Fireworks lit up the hazy sky over Sheshan International, and Molinari's older brother, Edoardo, was among those behind the 18th green ready to celebrate.
Until this year, the European Tour had never had more than one Italian win a tournament. Now there have been three in the last two months, starting with Edoardo Molinari at the Johnnie Walker Championship, and most recently Matteo Manassero.
"I was on tour the last few years basically on my own as an Italian," Francesco Molinari said. "So it was very good to see them this year coming through. And obviously, when they won, I wanted to win, as well. It made me work a little bit harder because I wanted to contribute to the golden moment of Italian golf."
Molinari, who earned $1.2 million, moved to No. 14 in the world ranking, three spots ahead of his brother.
Westwood was a runner-up for the fourth time this year -- including the British Open and the Masters. This gave him a larger cushion in the battle for No. 1 in the world, although he still could lose it when he next plays the Dubai World Championship in three weeks.
PGA champion Martin Kaymer shot 71 and tied for 30th. Masters champion Phil Mickelson had a 73 and tied for 41st. They are playing next week in the Singapore Open.
Woods remains at No. 2 and heads Down Under to defend at the Australian Masters.
"It wasn't really about the rankings," Westwood said. "It was about trying to win this week. The rankings come as a consequence of playing well, and I'm playing well. I know I am. Today is just very typical of how I've played for the last two years."