With the win, the 37-year-old Swede clinched the FedEx Cup and its $10 million bonus. Stenson also earned $1.44 million for winning the tournament.
Stenson made four bogeys in the rain on the back nine at East Lake and shot a 1-under 69 for a four-shot lead over Dustin Johnson.
No one expected another round like that from him — though Matt Kuchar had a 61 in the morning when conditions were calm.
Jim Furyk has become the sixth player in PGA Tour history to shoot a 59.
Scott played bogey-free and closed with a 5-under 66. He finished an hour before the final group.
Kuchar caught up by playing bogey-free on the back nine with three birdies, starting with a superb shot on the 10th to 3 feet.
While there are many other great and popular players on the American team — including Phil Mickelson, Bubba Watson, Steve Stricker and Jim Furyk — it is up to Woods to become the leader.
Snedeker collected $1.44 million for winning the Tour Championship, his second title of the year. And he won $10 million for capturing the FedEx Cup.
Thousands of fans chased after Woods and McIlroy, in the marquee group based on their standing in the FedEx Cup — Woods at No. 1 and McIlroy at No. 3. Both of them got off to a reasonable start.
Bill Haas made a stunning par save from shallow water, then won the high-stakes FedEx Cup on Sunday worth $11.44 million
Of the top five players in the FedEx Cup, only Luke Donald remains in serious contention. That means Mahan has a shot at the FedEx Cup and its $10 million bonus if he were to win the Tour Championship (and its paltry $1.44 million payoff).
Right when it looked as though Justin Rose might blow a big lead, he chipped in for birdie on the 17th hole to secure a two-shot victory Sunday in the BMW Championship that sends him to East Lake for a shot at $10 million.
Even as Cog Hill played tougher under sunshine and swirling wind, Rose made only one bogey as his top challengers fell apart. He wound up with a 2-under 69 and built a four-shot lead going into the final round at Cog Hill.
All three of them were outside the top 70 in the FedEx Cup standings, on the verge of being eliminated from the chase for a $10 million prize.
Webb Simpson made three big putts, the last one giving him an unlikely win Monday in the Deutsche Bank Championship.