Teen star Andreescu wins US Open as Serena Williams' bid for record-tying Grand Slam fails again
Andreescu, 19, produced a brilliant performance against six-time US Open winner Williams, sealing victory 6-3 7-5 at Arthur Ashe Stadium.
It is a maiden Grand Slam title for the Canadian, who becomes the first teenage winner of a Major since Russia's Maria Sharapova at the same venue in 2006.
For Williams, who is two weeks shy of her 38th birthday, it means she remains stuck on 23 Grand Slam titles, having now failed in her past four Majors finals, including twice at Flushing Meadows.
The match was billed as a battle of ages given the near 19-year age gap between the pair, and was played out in front of a fiercely pro-Williams crowd at Arthur Ashe Stadium.
Andreescu, however, showed no sign of nerves as the 15th seed broke Williams at the very first time of asking on her way to taking the first set.
She then raced into a 5-1 lead in the second set, only for Williams to incredibly battle back into contention and level the set 5-5.
But Andreescu defied the deafening home support for her rival to then hold serve and break Williams again, taking the set 7-5 and her first maiden Grand Slam with it.
Apart from her second set burst, Williams rarely looked like firing on all cylinders and was left to rue yet another missed opportunity at leveling Margaret Court's all-time tally of 24 Grand Slam titles.
Williams has now lost in successive US Open finals, following her defeat in such controversial circumstances at the same venue to Japanese youngster Naomi Osaka last year.
Andreescu, who had not even been born when Williams won her first US Open title 20 years ago, had said it was “surreal” to have reached Saturday’s showpiece in New York.
And she was taken even further into dreamland by clinching the title in what was the first time she has appeared in the main draw at the tournament.
The title also caps an incredible run of form which will see the Canadian catapulted to the dizzy heights of world number five, while becoming the first ever person from her country to win a Grand Slam singles title.