Janneman Malan struck a magnificent century in just his second ODI as South Africa cruised to the 272-run target with relative ease to complete a series win against Australia.
The well-settled opener combined with aggressive finisher David Miller to help the Proteas hold their nerve in the crunch moments of the match.
South Africa's unassailable lead in the three-match series ensures them their first series victory in any format in almost 12 months and bodes well for the future of new skipper Quinton de Kock and head coach Mark Boucher.
In the first innings, Australia's progress was hampered in the face of a blazing spell of bowling from Lungi Ngidi.
The right-arm paceman picked up six wickets for 58 runs, depriving the tourists of the impetus to fire on all cylinders in the latter half of the innings.
Australia stuttered to 271 all out, failing to find significant contributions from the lower-order after Aaron Finch and D'Arcy Short's identical scores of 69.
Malan made 129 not out in a wonderfully crafted innings, withstanding the visitors' much-feared pace attack. His three-figure score was a marked improvement from his golden duck on ODI debut in the first match in Paarl on Sunday.
The younger sibling of Test batsman Pieter Malan credited Jon-Jon Smuts, Heinrich Klaasen and Miller for giving him the confidence to carry on batting throughout South Africa's chase.
The Proteas were rocked by the early departure of de Kock but partnerships of 91, 81 and 90 followed the loss.
"They were great partners to have in the chase," said Malan. "My partners kept me calm when I was itching a bit."
On the other hand, Ngidi entered the record books by becoming the fastest South African to 50 ODI wickets in 26 games.
He halted Australia's momentum after David Warner and captain Finch gave them a brisk start. Ngidi managed to consistently knock out opposing batters just when it seemed they were in for a big score.
"I was given the challenge before the game by the coach (Mark Boucher) to knock over the big three," Ngidi later said
"When you've got 'in' batters batting right to the end it makes a huge difference," said Finch while lamenting the first-innings collapse.
The two teams will battle for the final ODI on Saturday with South Africa in with a chance to clinch a series sweep.