All-rounder Cameron Green took a career-best 5-27 as Australia ripped through South Africa's fragile batting before piling on late runs to seize control of the second Test in Melbourne on Monday.
After the visitors were dismissed for 189, an aggressive David Warner, in his 100th Test, was unbeaten on 32 and Marnus Labuschagne was not out on five to steer the hosts to 45-1 at stumps on day one.
Usman Khawaja was out for one, caught behind by Kyle Verreynne off Kagiso Rabada.
SCORECARD | Proteas v Australia - 2nd Test, Day 1
Australia won the first of three Tests by six wickets inside two days on a hostile and green Gabba pitch in Brisbane last week.
The wicket at the Melbourne Cricket Ground was less bowler-friendly, but captain Pat Cummins surprisingly chose to field at a venue where toss-winning teams normally bat first.
South African skipper Dean Elgar said he was bewildered by the decision, but it proved to be inspired in front of 64 876 fans with the Proteas losing early wickets as they again struggled against the hosts' bowling firepower.
After slumping to 67-5, Verreynne and Marco Jansen launched a stirring fightback in a gutsy 112-run stand.
But then Green - the second-most expensive buy at the Indian Premier League auction last week - went on a blitz, snapping the partnership when Verreynne got an outside edge on 52 that Steve Smith collected.
Two balls later, Jansen was gone, caught by wicketkeeper Alex Carey for 59 off Green before the giant Australian bowled Kagiso Rabada and Lungi Ngidi.
Green took 4-8 in the spell with the Proteas losing their last five wickets for 10 runs.
South Africa started the day nervously, losing Sarel Erwee and Theunis de Bruyn cheaply.
They were stunned just before lunch when Elgar, who passed 5,000 Test runs, and the experienced Temba Bavuma departed in consecutive balls.
It left them in trouble at 58-4 and the inexperienced middle order facing a daunting task.
When Khaya Zondo was out in the fifth over after lunch for five, courtesy of a stunning Marnus Labuschagne diving catch, the end looked nigh before Verreynne and Jansen dug in.
On a humid day, Cummins asked some searching early questions, dropping Elgar on seven off his own bowling and then having two big lbw shouts against Sarel Erwee denied.
Erwee lived dangerously and was no match for local hero Scott Boland.
The seamer, who took 6-7 in the corresponding Test against England a year ago, came on to thunderous applause and got the breakthrough in his second over, with Khawaja taking a low catch at third slip to remove Erwee for 18.
South Africa's batting has been under the pump recently and as the senior player, Elgar knew he had to stick around.
But it was a grind, with the captain surviving when an inside edge off Boland sent the ball rolling onto his stumps only for the bails to stay on, then being dropped by Nathan Lyon.
Green got Australia's second wicket when Theunis De Bruyn attempted a pull shot and wicketkeeper Carey took an easy catch.
Disaster then struck with a sluggish Elgar needlessly run out by Labuschagne going for a single on 26, and Bavuma fell for one next ball, edging Mitchell Starc to Carey after a poor shot.