Serena Williams embraces her fourth U.S. Open championship and 15th major title overall. (KEVIN LAMARQUE/REUTERS)

After breezing into Sunday’ s U.S. Open final without facing a credible challenge, Serena Williams ran headlong into a woman who hits as hard, competes as fiercely and wanted to win the season’s final major as much as she did.

Victoria Azarenka shook off her first-set jitters to stand up to Williams’s vaunted serve, yanked the American from one side of the court to the other and forced her into a rash of uncharacteristic errors.

But two points from defeat, Williams refused to buckle. She reeled off four consecutive games to win her fourth U.S. Open, 6-2, 2-6, 7-5, and collapsed on her back.

“I honestly can’t believe I won,” Williams told the 23,771 at Arthur Ashe Stadium after running to her courtside box to her hug mother and share the victory with her sisters and closest supporters. “I was preparing my runner-up speech, she was playing so great.”

It had been 17 years since a U.S. Open women’s final was forced to three sets, when Steffi Graf defeated Monica Seles to win the 1995 title. And this battle was riveting. The 23-year-old Azarenka threw every possible stroke at Williams in hopes of rattling the most dominant player in the women’s game. And Williams held nothing back through good stretches and bad, finishing with 44 winners (to Azarenka’s 13) and 45 unforced errors (to Azarenka’s 28).

In the end, it was Williams’s serve and experience that made the difference. She produced most of her 13 aces at critical junctures. And with Azarenka taking a 5-3 lead in the third set, Williams dialed back the risk on her shots ever so slightly, forcing her opponent, playing in only the second major final of her career, to win the title outright. And when Azarenka replied with the errors that were almost inevitable given the extraordinary stakes and stage, Williams capitalized.

Williams’s reward is a handsome $1.9 million in prize money and several notable distinctions to add to an already dazzling résumé.

Williams has now won 15 Grand Slam singles titles, putting her within range of matching the 18 held by Martina Navratilova and Chris Evert.

She’s the only woman to win more than one major this year, having claimed Wimbledon in July and the U.S. Open Sunday. (Azarenka won the Australian Open; Maria Sharapova, the French). She set a record for the number of years between major titles, with Sunday’s triumph coming 13 years after she hoisted the first of her four U.S. Open trophies in 1999, at age 17.

And regardless of the computer-generated rankings that put the 30-year-old Williams at No. 4 in the world, she is indisputably the best player in women’s tennis, with a 10-1 career record against world No. 1 Azarenka; a 9-2 career record against Sharapova, who’ll assume the No. 2 ranking on Monday; and a 3-0 record against world No. 3 Agnieszka Radwanska.

Sunday’s victory, Williams’s 44th in her last 46 matches, was an emphatic statement of Williams’s dominance and longevity.

And Azarenka, who outplayed her in stretches and twice was within one point for forcing a third-set tiebreaker, could only express admiration.

“Serena deserved to win,” Azarenka said during the trophy presentation that followed. “I’m just honored to stand with such a champion here.”

The match featured two of the sport’s hardest hitters and more formidable front runners. Azarenka was 48-0 when winning the first set in her matches this season; Williams was 48-1 when winning the first set.

Williams seized the upper hand quickly, breaking Azarenka twice in the first opening set to take a 6-2 lead.

But with her nerves settling and confidence growing, Azarenka came out stronger in the second set, while Williams’s serve lost its bearings. The American was broken to open the second set and fell behind 0-2.

Serving at 1-3, Williams double-faulted and netted an easy backhand. Azarenka charged the net, and Williams wildly over-hit a passing shot to get broken a second time. The Belarusan then held to become the first woman to win a set against Williams in the tournament.

The match knotted at one set each, Williams’s unforced errors mounted as her footwork deteriorated.

But after Williams had trailed 3-5, the crowd stood and cheered when the American pulled even at 5-5, sending the match into a third hour.

“It really, really hurts,” Azarenka said afterward. “Being so close, it hurts. But at this moment I have no regrets. I felt like I gave it all there. I feel proud of myself in one way, but definitely sad.”