Cameron Smith carded a nine-under-par 62 to set the early pace by one stroke after the first round of the RBC Heritage.
Australian golfer Smith turned in a bogey-free round at Harbour Town on Thursday for the lowest score of his PGA Tour career.
The 2020 Masters runner-up birdied three of the last four holes, just missing an eagle at the last when his approach shot missed the hole by inches.
Smith finished with nine birdies in the opening round, tying his career record for most birdies in a single round on Tour.
"Everything just came together," Smith told reporters. "It was a great day on the green. I was hitting my irons really good. I had lots of good looks, and I just took advantage of them."
Smith's score matched the lowest opening round in tournament history, joining Davis Love III in 2002 and Peter Lonard three years later.
The 27-year-old has two career PGA Tour titles, the most recent in January 2020 at the Sony Open in Hawaii.
"I just feel really comfortable," Smith said. "Mentally I feel very free out there. I feel like I can hit the shot that I need to hit and going ahead and trying to execute it. I just feel like every shot I'm hitting, I'm putting 100 per cent into it, and on a day like today, it's really rewarding."
Two-time champion Stewart Cink started early and was the clubhouse leader with a 63 before Smith's torrid closing stretch left him second on the leaderboard.
Cink's score on Thursday was the American veteran's best in 75 career rounds at Harbour Town.
"A round like this doesn't show you there is more out there," Cink said. "A round like this shows you what you're doing is already dead on, and why change anything?"
Matt Wallace and Collin Morikawa are three shots back at six under, followed by Charles Howell III, Billy Horschel and Harold Varner III – who are a stroke further adrift.
Masters runner-up Will Zalatoris shot a three-under-par 68, while world number one Dustin Johnson ended the day eight shots off the pace.
Defending champion Webb Simpson opened his bid for back-to-back titles with a first-round 71, leaving him tied for 67th.