* Swede seals victory with closing 68
* Also wins the $10 million FedExCup bonus
* Clinches second PGA Tour win of the year (Adds detail, further quotes)
By Mark Lamport-Stokes
ATLANTA, Sept 22 (Reuters) - Henrik Stenson held his nerve to fend off a last-day charge by Jordan Spieth and win the season-ending Tour Championship by three shots on Sunday, along with FedExCup honours and the mind-boggling $10 million bonus.
Four strokes in front overnight in the fourth and final playoff event, Stenson saw his lead briefly cut to one on the back nine before he birdied the 15th on the way to his fourth title on the U.S. circuit, and his second of the year.
The Swede, one of five players who came into this week knowing that victory would automatically secure him the playoff crown, signed off with a two-under-par 68 on a sun-splashed day at East Lake Golf Club for a 13-under total of 267.
PGA Tour rookie sensation Spieth, seeking his second victory of the year, closed with an eight-birdie 64 to finish in a tie for second at 10 under with fellow American Steve Stricker (65).
"Wow, it's been a great week and obviously a great playoffs for me," a beaming Stenson said after being presented with both trophies following his wire-to-wire victory. He also won the Deutsche Bank Championship earlier this month.
"It's been a great season, a great summer. This is going to sink in over the coming days. What better way to go into a month-long break than this?"
Stenson, the first European player to win either trophy up for grabs at East Lake, will earn a combined $11.44 million for his week as the Tour Championship purse amounts to $1.44 million.
"That's a fair amount," the 37-year-old Swede told reporters, after a brief pause to reflect on the numbers. "But it's definitely the second thing to me right now.
"Having these two trophies, with my fourth time (to win) on the PGA Tour and then to be the FedExCup champion, that means a whole lot more to me than the money."
American Webb Simpson carded a best-of-the-day 63 to secure fourth place in the elite 30-player field at nine under, a stroke better than compatriot Dustin Johnson (69).
FedExCup points leader Tiger Woods, a distant 14 strokes off the pace overnight, ended his 2013 PGA Tour campaign with a three-under 67 in a tie for 22nd at level-par 280.
The final round all boiled down to Stenson and whether his nerve and overnight lead would hold up as he chased the biggest payday of his career.
He safely parred the first, despite ending up in the right rough off the tee, but his lead was cut to three when playing partner Johnson sank a slick, 15-foot birdie putt at the par-four third.
Though Johnson bogeyed the fifth and sixth to slide back, Spieth began to apply pressure on Stenson with three successive birdies from the seventh.
However the Swede struck a superb approach to three feet at the seventh to pick up his first shot of the day, then parred the next two holes to hold a commanding five-stroke advantage at the turn.
Stenson also birded the 11th, draining a 10-footer, but Spieth continued to charge with a sizzling run of four consecutive birdies from the par-four 13th to move two shots off the pace.
The Swede was certainly feeling the pressure and he bogeyed the 14th after finding rough off the tee, overshooting the green with his approach and missing a 25-footer for his lead to be cut to one.
But Spieth stumbled with a bogey at the 17th after hitting his approach into a plugged lie in a greenside bunker and Stenson regained a three-stroke cushion with a birdie at the par-five 15th, where he got up and down from behind the green.
Stenson almost holed his bunker shot for an unexpected birdie at the par-four 16th, his ball finishing inches from the cup, then parred the last two holes to end his PGA Tour campaign on a lucrative high note.
"I'm just really happy with the way I stuck in there because it didn't feel the best today by far," said the Swede, a seven-times winner on the European Tour who will rise to fourth in the world rankings on Monday.
"To go out there and still shoot two under around a tough golf course is still a good score and a good accomplishment." (Reporting by Mark Lamport-Stokes; Editing by Gene Cherry)