NEW YORK, NY, USA - Coming into the US Open, the hot topic was the unstoppable comeback of Serena Williams, who had not lost a single match in the summer hardcourt lead-up. And that streak kept going at the big one, as she stormed through her first six matches in straight sets on Ashe Stadium.

But there was a quiet, historic revolution going on away from Ashe, one that would end up snapping the 13-time Grand Slam champion's streak and giving Australia its first women's Grand Slam singles champion in more than 31 years.

With a win on Court 11, two on Armstrong Stadium and three on Grandstand, a No.9-seeded Sam Stosur fought into her second Grand Slam final, and in her first match of the fortnight on Ashe she played one of the cleanest, most aggressive matches in recent memory to beat No.28 seed Williams, 62 63.

Stosur had beaten Williams twice before, including once at a Slam (at the 2010 French Open). Not many people were picking her to do it this time but with 20 winners to just 12 errors she pulled it off against a somewhat erratic Williams, who finished with similar winners, 19, but over twice the errors, 25.

The intensity of the match picked up early in the second set, when Williams was docked a point - thus giving Stosur a 62 10 lead - after letting out a victory cry on a big forehand up the line that had not yet become a winner, as Stosur still got her racquet on it. But those circumstances only seemed to energize Williams, who kept trying to fight back from that break down in the second set.

Williams faced her first two match points serving at 15-40 down 62 53, fending them off with an overhead winner and a big forehand that drew an error from Stosur - but the 27-year-old Australian cooked up two big inside out forehand winners on the next two points to close out the biggest victory of her career.

"I think I had one of my best days. It was fortunate to do it on this stage in New York, where I love to play," Stosur said at the trophy presentation. "I've dreamt about this since I started playing and even knew what a Grand Slam was."

Stosur elaborated on the match later. "I had to believe I had a chance. Having two victories over her in the past helped me feel it was possible. I was able to step up and hit my favorite shot - my forehand - off nearly every second serve she hit, which put her under pressure every time she missed a first serve.

"After that first set I sat down and could feel my heart pounding out of my chest. I thought, 'I'm up a set now, I've got a chance to win one out of the next two.'

"I can't believe I actually won this tournament. To go out there and play the way I did - you hope to be able to do that, but to actually do it is unbelievable."

Stosur, who lost to Francesca Schiavone in her first Grand Slam final at last year's French Open, now becomes the first Australian woman to win a Grand Slam title since Evonne Goolagong won Wimbledon in 1980. She is also just the second Australian woman in the Open Era to conquer the US Open, after Margaret Court (who won here three times, in 1969, 1970 and 1973).

Williams is now 13-4 in her career in Grand Slam finals, still quite an excellent record - however, this was her equal-worst loss in a Grand Slam final in terms of games won, tying her 61 64 loss to Maria Sharapova at Wimbledon in 2004.

Williams had to play her semifinal against Caroline Wozniacki late on Saturday night, with her post-match press conference not even starting until after midnight - but she gave all the credit for Sunday's win to Stosur.

"I was a little more tired than I expected, but I'm not here to make excuses. I want to give all the credit to Sam, because I think she played really, really well," Williams said. "I don't think it would have made a difference today. I just probably should have been lighter on my toes and moved a little faster.

"The last 14 months have been really hard. Six months ago I never thought I'd have even have a chance to play for the US Open, let alone seven weeks ago. I'm excited I'm healthy and alive, and still competing with the best.

"But every time I lose, I get better. So watch out."

Williams sat down next to Stosur after the final. "All of a sudden I turned around and she was right next to me, saying, 'How do you feel? Are you really excited?' It shows what a nice person she is and what a true champion she is of the sport," Stosur commented. "To separate the result a few minutes later and come over and congratulate your opponent, I thought was pretty classy."