Leishman shot a bogey-free six-under 66 in Thursday's first round at the Grange and is co-leader with American megastar Bryson DeChambeau.
DeChambeau's fellow major winners Dustin Johnson, who landed two eagles in his five under, and Jon Rahm (four under) lurk ominously.
Anthony Kim shares second place at five under, a shot ahead of  Abraham Ancer and Northern Ireland's Graham McDowell who both banked rounds of 68.
Leishman entered the opening round in the shadows of his compatriots Cam Smith and the emerging Elvis Smylie, who won on his LIV debut last weekend in Saudi Arabia.
Smith, after carding bogeys on his initial three holes, fought back to finish even par, while the 23-year-old Smylie shot three birdies in his two-under 70.
Fellow Australian and Ripper GC teammate Lucas Herbert finished one under after a rollercoaster round featuring three bogeys and four birdies.
Leishman had no such dramas in a superb start to the fourth edition of LIV's Adelaide tournament which is yet to feature an Australian individual winner.
The 42-year-old peeled off four birdies in a seven-hole stretch at the sandbelt course in Adelaide's beachside western suburbs.
And Leishman, chasing a second victory on the LIV circuit to follow his triumph in Miami last year, banked two more birdies on successive holes, the 16th and 17th.
His six under effort was one stroke shy of his best LIV round in Adelaide - he twice shot seven under at the Grange, in 2023 and '24.
Another Australian in the field, Adelaide's Wade Ormsby, who is a LIV reserve and was summoned to replace Phil Mickelsen who remains in the US because of family matter, finished one over on his home course.
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