Two-time major winner Dustin Johnson fired a nine-under par 63 to seize a three-stroke lead after Friday's opening round of the LIV Golf Chicago Invitational.
The 38-year-old American enjoyed a bogey-free 18 holes to start the 54-hole event at Rich Harvest Farms, with the winner set to collect $4 million from a $25 million purse.
"I struck the ball really well," Johnson said. "I hit it really close. I holed a lot of putts inside 10 feet."
Australia's third-ranked Cameron Smith, who won the British Open in July at St. Andrews, was second on 66.
"I was hitting good putts but they weren't going in," Smith said. "At the end they started going in. I hope I can keep it going."
American Matthew Wolff was third on 67 with Sweden's Henrik Stenson, England's Lee Westwood, American Charles Howell and Australian Matt Jones sharing fourth on 68.
"It was a good day," Howell said. "The wind picked up. It gets your attention on some of the holes."
The Saudi-backed upstart series has caused turmoil in the golf world as several big-name stars have defected from the US PGA Tour to the rival circuit, prompting the PGA to issue indefinite bans on former members.
Johnson, coming off his first LIV Golf victory two weeks ago at Boston, started off the first tee at the shotgun start and made birdies at the par-5 second and par-3 third holes.
Johnson, the 2020 Masters and 2016 US Open champion, reeled off four consecutive birdies starting at the sixth and followed by a 10-footer at seven, a 12-footer at eight and a six-footer at the ninth.
After finding greenside rough at the par-5 11th, Johnson chipped to two feet and tapped in for birdie, then sank a 10-foot birdie putt at 12.
Johnson was threatening the LIV Golf-record low round of 62 by England's Lee Westwood in the final round at Boston, but had five pars and a five-foot birdie putt at the 15th to close the round.
Johnson's lowest PGA round was an 11-under 60 in the second round in 2020 at TPC Boston on his way to winning the PGA Northern Trust.
It's the fifth of eight LIV Golf events this season, with October tournaments in Bangkok, Jeddah and a $50 million season-ending team championship at Miami.