Members of Australia's Wallabies rugby team celebrate their Bledisloe Cup win over New Zealand's All Blacks in Sydney, August 8, 2015.  [Photo/Agencies]

SYDNEY - Australia stunned world champions New Zealand 27-19 to claim a first Rugby Championship title in the fourth year of the competition and a welcome boost ahead of the World Cup on Saturday.

Nic White came off the bench to score a penalty and a converted try which settled a contest which had see-sawed back and forth for the best part of 70 minutes, giving the Wallabies a first win over the All Blacks since they won the final Tri-Nations in 2011.

Prop Sekope Kepu and winger Adam Ashley-Cooper also crossed for the Australians, who will win back the Bledisloe Cup for the first time since 2002 if they can beat their neighbours in Auckland next week.

New Zealand winger Nehe Milner-Skudder scored two tries on debut and flyhalf Dan Carter kicked three penalties but it was not enough to prevent the All Blacks falling to only a third defeat since winning the World Cup in 2011.

"You don't just say you've won once in quite a long time and you've done something special," Australia coach Michael Cheika said, trying to dampen down expectations.

"It's nice for the lads, but it's an abridged Rugby Championship so it's only the three games. We want to test ourselves over more games."

All Blacks captain Richie McCaw suffered only his 15th defeat in the black shirt as he made his 141st appearance for his country, matching Irishman Brian O'Driscoll's record tally.

"I think Australia played exceptionally well tonight and thoroughly deserved the win," said All Blacks coach Steve Hansen.