Dominant throughout most of the tournament, Serena Williams faced her toughest test at the U.S. Open on Sunday in the women's final against No. 1-ranked Victoria Azarenka.

After one easy set win for each player, Williams had her back against the wall, down 5-3 in the third set and two points away from losing the match. But she focused on her game and her serve, retaking the lead and never looking back as she defeated Azarenka 6-2, 2-6, 7-5 on Sunday night for her fourth U.S. Open title.

Williams won the last four games of the set to take the win. The match lasted for 2-hours and 18-minutes.

"I never, never quit. I have come back so many times in so many matches," Williams told the Associated Press. "I wasn't too nervous."

It was her 15th Grand Slam singles win and also allowed Williams to pass the $40 million earnings total, a feat no women's player had ever accomplished.

"I honestly can't believe I won. I really was preparing my runner-up speech, because I thought, 'Man, she's playing so great,' " Williams said during the trophy presentation adding: "I'm really shocked."

Coming into the match, Williams had not dropped a set in the tournament and had only lost 19 games overall. Both players had also been undefeated this year in three set matches, before Williams won and improved to 11-0.

In her career, Azarenka was only 1-9 against Williams and had lost to her this year in Wimbeldon and at the Olympics. Williams went on to win both of those tournaments.

Following her loss at this year's French Open, Williams has gone 26-1, winning a gold medal and two Grand Slams.

"I was miserable after that loss in Paris. I have never been so miserable after a loss," Williams said. "I pulled it together. ... Sometimes, they say, it's good to lose."

Williams easily won the first set against Azarenka on Sunday, but was down 4-1 in second set where she was broken twice. Azarenka took the set to force a third frame to decide the champion. It was the first time the women's final had gone to a third set since 1996 between Stefi Graf and Monica Seles.

Williams went up a break on Azarenka after being down 40-15 before the set got tied up at 3-3. She began to struggle with her serve midway through the set, giving Azarenka triple break point and the lead at 4-3.

In the next game Azarenka was serving up a break and was tied 30-30 when she had a wide open court shot she could have made, but put the ball into the net, giving Williams a break point. But Azarenka held her composure, and smashed a forehand winner down the line to go up 5-3.

Up to that point in the match, Williams had twice as many forehand errors as winners. Williams was forced to serve to stay in the match and held after winning on a hard forehand winner down the right baseline.

Azarenka was serving for the championship but struck three straight errors to give Williams a triple break point. On the second break point Azarenka hit the ball into the net to tie it up at 5-5. The crowd went wild as Williams set up to serve the next game.

After winning seven of the last eight points, Williams hit a hard serve that Azarenka put into the net to bring it to 6-5.

"Feels like there is no room for a mistake," is the way Azarenka described trying to deal with Williams' game. "There is no room for a wrong decision."

Azarenka had a chance to serve and force a third set tiebreak, which would have been the first in a women's final since 1985. Williams hit an amazing forehand winner past Azarenka down the line to bring it to 30-30, after which Azarenka hit a chip drop shot to go up 40-30.

Williams hit a cross court winner off a second serve to bring things to deuce and then went up an advantage when Azarenka hit a ball long. On match point Azarenka faulted once, then hit another shot long to finally end it.

Williams fell directly onto the hard court and started to celebrate before the two players shook hands at the net. Azarenka couldn't help but go bury her face under her towel directly after, but was very gracious and respectful in the post-match interview.

The crowd erupted as the match ended and Williams climbed over to her family box to share in the excitement with her sisters, including Venus Williams.

Williams became the first 30-year-old woman to win the championship since Martina Navratilova in 1987. She has now won four U.S. Open titles in her career, including one as a 17-year-old in 1999, and then in 2002 and 2008.

She also became the first woman since herself in 2002 to win both Wimbeldon and the U.S. Open in the same season.

Williams used a dominant serve throughout the tournament and also on Sunday to help propel her to victory. She finished the match with 13 aces, while Azarenka had none.