Jean van de Velde, the winner of this year's Madeira Island Open and the man who famously threw away the 1999 British Open, and Stephen Gallacher are knotted in second place at 4-under-par 68.
Eight-time Order of Merit champion Colin Montgomerie, Thomas Bjorn, Peter Lawrie, Marcus Fraser, Frankie Minoza and this year's Malaysian Open winner Charlie Wi are tied for fourth place at minus-3 at Tomson Shanghai Pudong Golf Club.
Stenson, the highest-ranked player in the field at No. 15, began on the 10th tee Thursday and collected his first birdie one hole later at the par-4 11th.
He added back-nine birdies at 13 and 16 to make the turn at 3-under-par 33.
The 30-year-old, who vaulted up the world rankings thanks to a runner-up finish at the Abu Dhabi Golf Championship, then a win at his next start, the Qatar Masters, promptly traded a birdie and a bogey at the second and third holes.
Stenson rebounded at the fifth with a birdie to reach 4 under par. He found water at the seventh hole, but was able to get up and down and save an unlikely par.
Stenson birdied the par-3 eighth to separate himself and take sole possession of the lead.
'It was dead calm,' said the Swedish Stenson, referring to the optimum scoring conditions in Thursday's opening round. 'The greens are putting well and the sun is shining.'
Stenson's start of the 2006 campaign rocketed him up the world rankings, but things have since cooled for the three-time winner on the European Tour. It might have to do with his relocation.
He went to the United States to prepare for The Masters, and despite a tie for third place at The Players Championship, struggled. Stenson made the cut at the Nissan Open, but tied for 77th. He tied for 17th at the WGC-Accenture Match Play Championship, played well at Sawgrass, then missed the cut in back- to-back weeks at the BellSouth Classic and at Augusta.
Stenson, who tied for 20th last week at the China Open, believes Thursday's play could be a stepping stone in returning to the winner's circle again this season.
'I had birdie chances on virtually every hole and knocked a few of them in,' said Stenson. 'Hopefully we're moving in the right direction and I can keep it up tomorrow.'
Van de Velde also started on the back nine Thursday and was 4 under through his first 11 holes. He made a 'silly' bogey at the eighth hole, but atoned for the miscue with a three-foot birdie putt at the ninth to get within one of the lead.
'The conditions were ideal and I knew it was a morning to put it together if you could,' said Van de Velde.
Gallacher birdied three in a row from the 11th, his second hole, and reached 5 under par thanks to back-to-back birdies from the first. He bogeyed No. 4 and parred out his remaining holes to join Van de Velde in second place.
Paul Lawrie, who went on to victory at that 1999 British Open, Francois Delamontagne, Alessandro Tadini, Ted Oh, Wen-chong Liang, Scott Drummond, Boonchu Ruangkit and Chapchai Nirat tied for 10th place at 2-under-par 70.
The Golf Channel will televise all four rounds beginning Thursday at 9 a.m. (ET).