Australia reached their eighth successive Netball World Cup final after edging a 55-53 win against South Africa in Liverpool.
The 11-time winners squandered an eight-goal half-time lead as the Proteas stormed back to within one with four minutes remaining.
But the Diamonds held on to reach Sunday's gold-medal match.
Australia now play New Zealand in Sunday's final as they bid to win their fourth consecutive title.
The Kiwis beat England 47-45 in the other semi-final on Saturday.
"I'm proud of them. They're a bunch of fighters. They played smart when we needed it and that's exactly what we have to do in pressure games," said Australia coach Lisa Alexander.
Having sailed through the first five matches of the group stages, Australia only just came through their match against trans-Tasman rivals New Zealand by a single goal to set up a meeting with South Africa.
As the world's best side, they were firm favourites to progress against a team ranked four places below them on Saturday.
Diamonds coach Alexander made some big calls with her starting line-up, opting for a completely fresh shooting partnership in Caitlin Thwaites and Gretel Tippett, and it paid off in the first half.
The Australians looked at home on the big stage and their confidence came through in the second quarter. They patiently turned the screw and pushed into a 31-23 lead at half-time, with both shooters finishing on 100% accuracy.
The Proteas were well beaten by England in their last group match but did not want to settle for second best in this semi-final.
Goal defence Karla Pretorius produced a number of aerial intercepts, as did goal keeper Phumza Maweni, who had by far her best game of the competition - while Lenize Potgieter was able to convert as South Africa pounced on turnovers.
However, even against a team playing out of their skin, a fired-up Australia attack can always find a way through.
They made three substitutions in the final quarter and never panicked - even when their lead was cut to one.
Ultimately, South Africa's inexperience of playing in their first semi-final was exposed by Australia, and the occasion was a step too far for Norma Plummer's side, who will now play England in Sunday's bronze-medal match (14:30 BST)
"I'm absolutely delighted for where we've taken the number one team in the world," said 74-year-old Plummer, who went on to confirm she would step down at the end of the tournament.
"We could still get a medal. Tomorrow is my 50th Test match with South Africa, and then I'm handing over the reins. I've done four years and shown them the way. It's up to them now."