Leishman strung together four birdies in a row from the seventh through the 10th holes on the par-73 Plantation Course at Kapalua on Maui.
He rolled in a 19-foot birdie putt at the 17th to take sole possession of the lead, with American Brian Harman and Venezuela’s Jhonattan Vegas sharing second on 68.
It was a further stroke back to world number one Dustin Johnson, Rickie Fowler and South Korean Kim Si-Woo on 69.
“Pretty solid,” Leishman said of his round in the first USPGA Tour event of the calendar year, which features a 34-player field made up of last season’s tournament winners.
“I played well, drove the ball pretty well — with the exception of a couple of drives — and the putter was really, really solid.
“So, happy with eight birdies,” added Leishman after a day that saw strong winds buffet some of the bigger names in the field.
Defending champion Justin Thomas, whose victory here last year marked the start of a five-win season that included his first major title and the FedEx Cup playoff crown, carded a two-under par 71.
British Open champion Jordan Spieth struggled to a two-over par 75.
Fowler eagled the final hole as he bounced back from a double-bogey at the 13th, and Johnson birdied the par-five 18th to seize his share of fourth place.
Leishman got off to a crisp start, rolling in a five-foot birdie putt at the first hole.
He hit nine of 15 fairways on the day and 15 of 18 greens in regulation.
The 34-year-old Australian enjoyed his best PGA Tour season of his career last season, winning the Arnold Palmer Invitational and the BMW Championship.
In October, he was runner-up in a playoff to Thomas at the CJ Cup @ Nine Bridges in South Korea.
While Leishman said his recent strong results didn’t mean he was “owed anything” in 2018, he said he was looking forward to the year with confidence.
“It’s not a given I’m going to play well,” he said. I’ve got to keep working, but confidence certainly makes it easier to play well.”
Leading first-round scores
67 — Marc Leishman (AUS)
68 — Brian Harman, Jhonattan Vegas (VEN)
69 — Kim Si-Woo (KOR), Rickie Fowler (USA), Dustin Johnson (USA)
70 — Billy Horschel (USA), Patrick Cantlay (USA), Kyle Stanley (USA),
Kevin Kisner (USA), Hideki Matsuyama (JPN)
71 — Ryan Armour (USA), Brendan Steele (USA), Jason Dufner (USA), Jon Rahm (ESP), Justin Thomas (USA)
72 — Patton Kizzire (USA), Chris Stroud (USA), Hudson Swafford (USA), Pat Perez (USA), Xander Schauffele (USA)
73 — Bryson DeChambeau (USA), Adam Hadwin (CAN), Daniel Berger (USA)
74 — Austin Cook (USA), Grayson Murray (USA), Wesley Bryan (USA), Kevin Chappell (USA), Russell Henley (USA)
75 — Cameron Smith (AUS), Jordan Spieth (USA)
76 — D.A. Points (USA)
77 — Jonas Blixt (SWE)
78 — Brooks Koepka (USA)
