|Australia (15) 30|
|Tries: Ikitau 2, Koroibete 2; Cons: Cooper 2; Pens: Cooper 2|
|South Africa (12) 17|
|Try: Am; Pens: Pollard 4|
Len Ikitau and Marika Koroibete scored two tries apiece as Australia secured a second successive victory over world champions South Africa in the Rugby Championship in Brisbane.
Ikitau touched down twice in the first half, although the Springboks took the lead through centre Lukhanyo Am two minutes into the second half.
Koroibete struck twice in six minutes to seal a bonus-point Australia win.
They are third in the table, one point behind second-placed South Africa.
New Zealand are five points clear at the top after winning their first three games.
South Africa will lose their world number one spot if New Zealand beat Argentina by more than 15 points in Saturday's second match at the Suncorp Stadium.
"We were really beaten," said South Africa coach Jacques Nienaber.
"We got hands down beaten in everything - defence, kicking game, attack. This isn't a performance that was worthy enough for a Springboks performance."
Soon after South Africa scrum-half Faf de Klerk was shown a yellow card for slowing the ball in a ruck, Ikitau sprinted past two defenders to score the opening try.
Ikitau crossed for a second time in the 21st minute following Koroibete's off-load, before De Klerk's return rejuvenated the Springboks as they trimmed the deficit to three points by half-time.
With Wallabies flanker Lachie Swinton yellow-carded for a high tackle on Duane Vermeulen, the visitors quickly snatched the lead after the restart when Am touched down.
However, Australia regained the initiative thanks to winger Koroibete, whose first try was created by Taniela Tupou's audacious no-look pass.
Koroibete's second established a 13-point lead and Australia defended it stoutly, repelling waves of South African attacks in the closing stages to see out a victory - seven days after their dramatic 28-26 win in Brisbane.
Australia face Argentina in their next two games.
Australia: Banks, Kellaway, Ikitau, Kerevi, Koroibete, Cooper, White, Slipper, Fainga'a, Tupou, Rodda, Philip, Swinton, Hooper, Valetini.
Replacements: Kaitu'u, Bell, Robertson, Swain, Samu, McDermott, Hodge, Petaia.
South Africa: Le Roux, Nkosi, Am, De Allende, Mapimpi, Pollard, De Klerk, Nyakane, Mbonambi, Malherbe, Etzebeth, Orie, Kolisi, Mostert, Vermeulen.
Replacements: Marx, Kitshoff, Koch, Van Staden, Smith, Wiese, Jantjies, Willemse.