South Africa are one win away from becoming the best Test side in the world after condemning Australia to a first series defeat on home soil in almost 16 years following a nine-wicket victory in the second Test at the MCG.

The Proteas - led by a fluent 75 from captain Graeme Smith - overhauled a modest victory target of 183 for the loss of only one wicket on the final day to take an unassailable 2-0 lead and seal a first-ever Test series triumph in Australia.

Hashim Amla, a man not burdened by scars from previous defeats to the hosts, stroked the winning runs shortly after lunch as South Africa became the first team to overcome Australia at home since the West Indies in 1992-93. That was also the last occasion Australia lost back-to-back Tests at home.

The days of South Africa squandering winning positions against their illustrious opponents now appear to be gone, while Australia's 13-year reign at the top of world cricket could also soon come to an end. Another loss in the final Test in Sydney, which would see Australia whitewashed for the first time in a series since 1984 against the West Indies, would see Ricky Ponting's side officially unseated by their opponents in the world rankings.

Jacques Kallis, who has been on the end of some stinging losses at the hands of the Australians, said the feat was just as big, if not bigger, than winning the World Cup.

Kallis, who picked up his 250th Test scalp during the match and is now only 53 runs away from becoming the eighth man to reach 10,000 runs, could barely hide his excitement at his team's performance. "At the MCG, what better place to want to do it," he said. "I've had some individual high moments here but this one takes the cake. Having won a Test match here beats all those feelings, it's an unbelievable effort."

The bowler said there were still some nervous moments in the dressing room despite the relatively small run chase. "I don't think it's ever easy when you're chasing a total," he said. "There's always anxious moments."

Smith, meanwhile, was lost for words as he gave his victory speech. "It has been such a special moment for all of us, it has been an incredible team effort," he said. "I have been smiling non-stop since we hit the winning runs. To be 2-0 up after this game was something we only dreamt of."

South Africa were never under any pressure in their run chase.

Needing a flurry of wickets early on the final day to have any hope of winning, Australia did not make a breakthrough until 16 minutes before lunch when Smith was trapped lbw by a Nathan Hauritz arm ball.

Smith had dominated a 121-run opening stand with Neil McKenzie and it was a shame for the Proteas skipper he was not there at the end having once again shown the kind of leadership befitting a man who was made captain of his country at the tender age of 22.

He cashed in on Australia's attacking approach, striking seven of his ten boundaries with cuts and deflections through a vacant third man region.

However, Smith was unexpectedly the first to go as the captain had previously been untroubled at the crease with partner Neil McKenzie appearing the most vulnerable of the pair.

While unconvincing, McKenzie - who had made scores of two, 10 and zero in his three most recent innings - dug in and managed to eke out an unbeaten 59.

He survived strong lbw shouts from Brett Lee, who was bowling despite nursing an injured foot that will keep him out of the Sydney Test, and Mitchell Johnson.

Poignantly, he reached his half-century with a boundary after being missed by another out-of-form opener Matthew Hayden at first slip off Johnson's bowling.