Flavia Pennetta beat countrywoman Roberta Vinci 7-6 (7-4) 6-2 to win the US Open in Saturday's all-Italian final at Flushing Meadows.
After Friday's incredible drama, which saw Pennetta eliminate second seed Simona Halep and Vinci pull off an even greater upset over world number one Serena Williams, it was left to the two Italians – and good friends – to decide the championship.
The match was very much a tale of two sets, with Vinci proving very competitive at first, only to run out of steam in the second.
After the first four games of the match stayed on serve, Pennetta made her move during a marathon fifth game that may have gone some way towards deciding the winner.
Pennetta applied heaps of pressure on Vinci's serve during that game, and after six spurned break points, she finally succeeded on her seventh.
But serving at 4-3, Pennetta handed Vinci just one break point, and the diminutive world number 43 immediately snatched it to level the scores once more.
It was left to a tie-break to decide the first set, and it was Pennetta who won the points that mattered, earning two set points and clinching the second.
Vinci appeared to tire after that, handing her opponent two easy breaks early in the second set as Pennetta raced to a 4-0 lead.
There was hope of a Vinci fightback when she regained one of those lost breaks, but serving at 2-5 to stay in the match, Pennetta played a dominant final game, winning it to love to seal what is by far the biggest win of her career.
Pennetta has been a WTA player since 2002 and reached her highest ranking of 10th in the world in August 2009.
She suffered a wrist injury in 2012 which saw her drop out of the top 50, but she did not give up and mounted a comeback that saw her reach the quarter-finals of the Australian Open in 2014.
Nothing could have prepared her for what happened in New York over these last two weeks, however, and the 33-year-old delivered a bombshell in her on-court interview after the match, revealing that she plans to retire immediately following her US Open win.
"I'm really happy," she said. "I never thought I would get so far, I never though I would be a champion. This is one of my favourite tournaments, I enjoy playing here. I really appreciate what my team did for me. It's a dream come true, and it's also nice to play with a friend of mine – we have known each other since we were really young, we spend so much time together we could write a book about my life.
"Before I started this tournament one month ago, I decided that this is the way I would say goodbye to tennis. This is my last and I couldn't think of finishing in a better way."
For Vinci, she was perhaps too spent after her epic encounter against Williams on Friday.
"Grazie! It was tough, I passed the 24 hours with a lot of things on my mind. But I am really happy and really happy for Flavia," she said in her on-court interview. "It's tough to play against a player who you have known for a long time. I tried to play my best, but Flavia played unbelievable and I have to say congrats to her."