New York: For Flavia Pennetta, summing up her tumultuous, shocking, fascinating and heart-warming US Open triumph was easily described in a single word.

"Perfect."

Pennetta, the oldest maiden Grand Slam finalist in the Open era, became the first Italian to win the US Open women's crown and did so on Saturday with an efficient 7-6(4), 6-2 victory over childhood friend and compatriot Roberta Vinci.

Before accepting the trophy and $3.3 million for the win that easily marked the greatest triumph of her career, the 33-year-old announced her retirement.

"My life is perfect," Pennetta said when asked how she would look back at the championship. "Perfect.

"This one was my last US Open match and I couldn't think to finish in a better way."

Two weeks ago, no one could have predicted a final between the 26th-ranked Pennetta, then rated a 150-1 outsider, and the 43rd-ranked Vinci, an even more unfancied 300-1. However, both players refused to be swayed by the odds and fought their way through to the most unlikely title showdown that put Italy firmly in the spotlight of New York's gaze.

Pennetta, who is engaged to fellow Italian tennis player Fabio Fognini, said she would play to the end of this season, including tournaments in Wuhan, Beijing and possibly the elite eight-woman WTA Finals in Singapore.

Adding to their collective joy, Fognini also had a magical moment at the Open, coming back from two sets down to eliminate 14-time Grand Slam winner Rafael Nadal in the third round with an inspired performance. Having battled injuries on a regular basis in recent years, Pennetta said she made the decision to call time on her career at last month's Toronto event.

"Sometimes it's getting hard for me to compete. This is the important point," she explained. "When you are in the court, when you have to play 24 weeks in the year, you have to fight every week.

"And if you don't fight every week in the same way I did today, it's gonna be bad. I don't feel to have this power anymore sometimes.

"So this is the perfect moment, I think. Was a really hard decision to make, but I'm really happy that I did it. I'm really happy and proud of myself."

Pennetta, who had previously climbed as high as 10th in the rankings in 2009 but will shoot up to eighth after this success, always seemed to save her best Grand Slam performances for the US Open.

Prior to this, she was a semi-finalist in New York in 2013 and reached the Flushing Meadows quarter finals on four other occasions. "I think I did everything that I expected," she said about her career. "More. Much more."

There to congratulate both Italians was Italy's Prime Minister Matteo Renzi. "He said: 'You won't understand what will happen now in Italy. It's good that you are here because it's going to be crazy back in Italy now. It's good to stay here a few days, just relax a little bit and then go back home.'"

Making the occasion extra special was sharing the stage with Vinci, who had miraculously overcome world No.1 Serena Williams with a stunning semi-final victory that crushed the American's dream of completing a calendar Grand Slam.