Williams outlasted World No. 1 Victoria Azarenka 6-2, 2-6, 7-5 on Sunday to win her fourth US Open crown, becoming its second-oldest Open-era winner at age 30, and a 15th Grand Slam title, seven shy of Steffi Graf's all-time record.
"Even though I'm 30, I feel so young and I've never felt as fit and more excited and more hungry," Williams said.
"Even with this win like I'm sitting here so excited still to play the next Grand Slam and see what I can do. I love that feeling. I feel like it's overdue."
Williams took her third major title in as many months after Wimbledon in July and Olympic gold last month on the same All England Club grass courts.
"It's so cool. I'm so excited," she said. "To cap off the gold medal and then to come from the gold medal to win US Open is unforgettable."
Williams won her first back-to-back Slam crowns since she captured four in a row -- the "Serena Slam" -- from the 2002 French Open through the 2003 Australian Open.
And she said if she had not missed 10 Slams with injury, she might have won five more by now.
"Yeah, I think so, but there's nothing I can do about that," she said.
Williams has won multiple Grand Slams in a season for the third time in four years, her 2010 and 2009 doubles coming at Wimbledon and the Australian Open.
Now Graf's mark seems reachable.
"I never thought I would even come close to breaking those records but if I can play consistently and play some more matches at Wimbledon, then it will be awesome," she said. "If I could win two a year it would be great. We'll see.
"I will think about my legacy when I'm done. I have so much more I want to create for the history."
There was a time not so long ago when Williams wondered if she might ever play again, much less recapture her championship form.
Williams battled back from a right foot injury that kept her from playing in the 2010 US Open and battled blood clots last year that jeopardised more than her career.
She fought back into form earlier this year but crashed out of the French Open with a first-round loss to Virginie Razzano, her worst-ever Grand Slam performance and her only 2012 loss in 50 matches where she won the first set.
"I have never been so miserable after a loss," Williams said. "I felt like I lost a little confidence after that. But finally I pulled it together.
"A champion is defined not by their wins but by how they can recover when they fall. I've fallen several times. Each time I just get up and I dust myself off and I pray and I'm able to get back to the level that I want to be on.
"So I feel really awesome I've been able to do that."
Since then, Williams has gone 26-1 with Wimbledon and US Open titles and an Olympic gold medal.
While Azarenka will remain World No. 1 in Monday's new WTA world rankings, Williams has showed beyond all doubt she is for now the true queen of tennis.
"Without doubt, she's the best player in the world right now regardless of what the WTA rankings say," Patrick Mouratoglou, the French coach who has worked closely with Williams since her French Open loss, told AFP.
"I knew she was capable of doing what she did today, but that doesn't make it any less exceptional. There was more pressure on her here than anywhere else, 100 times as much. She refuses to accept defeat."