World No.1 Serena Williams has matched Roger Federer's all-time men's grand slam titles record with victory over second-ranked Victoria Azarenka in the longest women's US Open final in more than 30 years.
Williams equalled Federer's 17 career majors with a 7-5 6-7 (6-8) 6-1 victory in a marathon final lasting two hours and 45 minutes on Sunday.
"Yeah, that's pretty cool," Williams said after drawing level with the great Swiss.
The 31-year-old American also became the oldest open-era women's winner in New York - 293 days older than Margaret Smith Court when the Australian won in 1973.
Williams won $US3.6 million ($A3.94 million), including a $US1 million ($A1.09 million) bonus for her success in US open tune-up events.
Williams won a rematch of last year's US Open final that gave her and Azarenka a combined total of six of the eight major titles from the past two years.
Williams improved to 13-3 in their rivalry but two-time Australian Open champion Azarenka had won two of the previous three, most recently in last month's Cincinnati final.
"It was never over until match point," said Williams, who was broken twice in the second set when serving for the match.
"Victoria is such a great competitor. She was really able to push me into a third set. I was really stern with myself. I knew that if I wanted to win, I had to play better."
Azarenka admitted Williams was the superior performer in windy conditions at Arthur Ashe Stadium that baffled both players at times and sent Williams' pink dress fluttering above her waist much of the match.
"It's a tough loss but being in the final against the best player, who deserves the win, it's incredible," Azarenka said. "I gave it everything I had. I fought hard."
Williams matched Steffi Graf for second on the open era list with five US Open trophies, one shy of Chris Evert's record, and moved one adrift of Martina Navratilova and Evert for second on the open era slam win list.
Graf has the open-era record of 22 while Smith Court owns the all-time mark of 24.
The two-and-three-quarter-hour match was the longest women's final since timing began in 1980, five minutes longer than the old mark set in 1981 when Tracy Austin outlasted Navratilova 1-6 7-6 (7-4) 7-6 (7-1).
"I haven't taken any of it in yet. I feel like it's deuce right now," Williams said 45 minutes after the match. "I feel like a zombie. I feel like there's another match."
Williams became the first woman since Justine Henin in 2007 to win the US and French Opens in the same year.
With the victory, Williams has won more than $US9 million ($A9.84 million) in 2013, a one-year women's record, and boosted her career winnings above $US50 million ($A54.65 million) as well as capturing her ninth title of the year, a one-season personal best.
She also has 55 career titles in total.
Williams, who lost only 16 games over her first six matches, battled windy conditions and a determined foe in a rematch of last year's final to add to the New York hardcourt trophy haul that included wins in 1999, 2002, 2008 and 2012.
Williams said her slam triumphs mean more after suffering blood clots in her lungs in 2011 that jeopardised her life and left her at times "lying in bed and thinking I will never play again".
"It's definitely sweeter," she said. "When I was 17 and won my first time I was really happy. Yet there were times I thought I would never pick up a racquet again so every one feels greater."