In a re-match of the last three Olympic finals, Australia played some outstanding Basketball in the first half to lead 47-43 at the break.
But the USA, who have never lost to Australia in 16 meetings, came out strong in the second half and then wore the Opals down late on to make the final 86-73 scoreline look much easier than it was.
Win number 40 came almost 20 years to the day after the streak began with victory in the 1992 bronze-medal game against Cuba in Barcelona.
Australia began to nose in front in today's semi-final after Kristi Harrower hit the first three-pointer of the game to make it 28-24 early in the second quarter, before a 7-0 burst put them on top 39-32.
The USA came back but Liz Cambage was proving a huge problem for the USA inside, and the Australians kept going to their tall centre and she kept them in front, making it 43-38 with a lay-up.
Australia led 47-43 at the break but the second half started with the USA on a charge.
Diana Taurasi's three-pointer got them started and they edged clear on another long-ball from the guard after Cambage missed a pair of free throws.
Australia's Lauren Jackson, who became the all-time leading scorer in Olympic women's Basketball history earlier in the Games, hit a three to close it to 55-54 and the Opals then led.
But that would be their last lead, as Lindsay Whalen took over the game for the USA, scoring six straight points to make it 61-56.
Tina Charles scored back-to-back baskets to end the third period and Seimone Augustus gave them a 67-59 lead with the first points of the final quarter.
Harrower's three gave Australia hope, but Augustus hit a long jump-shot and then a turnover gave Moore a free run to the basket to make it 71-62, with the Opals seeing their challenge rapidly fading down the stretch.
Taurasi and Charles had 14 points each for the USA, with Charles adding 10 rebounds. Bird collected 13 points.
Cambage, so instrumental in the first half, could not make a shot in the second half, with all 19 of her points coming before the break.