Tournament host Woods meanwhile came back strongly after his disappointing 72 on Wednesday, hitting a bogey-free 66.
Patrick Reed edged into a three-shot lead at the Hero World Challenge in the Bahamas on Thursday as Tiger Woods bounced back into contention after a lacklustre opening round. "I'm not going to give it a 10, but close to a nine out of 10".
To sum up the situation, his ball was sat in a sanded waste area and it was decided that he had improved his lie prior to playing his next shot.
Rahm, who had started the day one shot off of Stenson, carded a six-under-par 66.
He drilled a 5-wood from 259 yards to within inches of the hole for a tap-in eagle on the par-5 15th, going from a one-shot deficit to a one-shot lead.
The former Open Champion started one stroke behind overnight leader Gary Woodland, and opened up his final round with a before adding two more at the seventh and eighth to gain the lead on 15-under-par. After years of looking much older than his age, Woods has seemingly (and improbably) found some sort of fountain of youth as heads off to captain the United States Presidents Cup team and rolls into 2020.
Second-placed Stenson hit a series of superb iron shots reminiscent of the form he displayed to win the 2016 British Open in a head-to-head duel with Phil Mickelson.
"Yes, I have spoken to Pat about it, it's behind us, we're onto this week, we're focused on going against this great worldwide team here", the 15-times major victor told reporters at the official launch of the tournament. "I can certainly compete with the best and I guess I showed that once again".
He finished at 18-under 270 for his first victory since August 2017, though it will be unofficial for record purposes on the PGA Tour due to the small 18-man field. He was then pushed down by Woods, Justin Thomas and Rahm in turns. Woods has never outscored Thomas in the 13 times they have played together, including the third round here.
Stenson briefly joined Woodland at the top when he made a strong putt to birdie on the par-4 13th hole.
Woods is tied third alongside fellow-American Justin Thomas and "European Tour Player of The Year" Jon Rahm.
"We're going to be locked up in a tin can for 23 hours, so we're just going to enjoy the ride down there and do a little bit of talking, a couple of meetings here and there on the flight so we all have an understanding of what our roles are going to be down there", he said. "I've been top 10 in the world for five or six years straight, and that's where I want to be".