The Canadian teenager Bianca Andreescu has beaten Serena Williams in straight sets to win the U.S. Tennis Open in straight sets.
Ranked 178th in the world at the start of year, Andreescu overcame a dramatic second-set collapse to deny Williams a record-equalling 24th grand slam singles crown with a 6-3 7-5 win in New York.
It was just the fourth grand slam tournament Andreescu had competed in.
She failed to get past the first round of qualifying at the two previous U.S. Opens.
Both Andreescu and Williams will compete in January ASB Classic in Auckland.
Title success on her main-draw debut at Flushing Meadows marked the equal- fastest journey to grand slam glory in tennis history, matching Monica Seles' feat in winning the 1990 French Open in only her fourth major.
The fearless 19-year-old is also the first Canadian to win a singles grand slam and first teenager to hoist the US Open trophy since Maria Sharapova in 2006.
"It's so hard to explain in words but I'm just beyond grateful and truly blessed," Andreescu said after improving her record over top-10 rivals in 2019 to a remarkable eight from eight with her third title of the season.
"I've worked really hard for this moment. This year has been a dream come true and now, to play Serena on this stage, a true legend of this sport, is amazing."
Not even born when Williams won the first of six titles in New York in 1999, Andreescu defied the doubters with an extraordinary baseline barrage as Williams once again crumbled under pressure trying to match Margaret Court's 24 singles slams.
It was the fourth consecutive grand slam final defeat for the American since returning from maternity leave after the birth of her daughter Olympia in September 2017.
But this one will likely hurt most with Williams injury free and finally back to full fitness, adamant pre-match she'd never been better prepared to return to the grand slam winners' circle.
After also falling to Naomi Osaka in last year's final and to Angelique Kerber and Simona Halep in the past two Wimbledon deciders, time may be running out for Williams - who turns 38 this month - to catch Court.
But she was gracious in defeat.
"Bianca played an unbelievable match, so congratulations. I'm so proud and happy for you," Williams said after her fifth loss from her past six grand slam finals - after winning 23 of her first 27.
"Yeah, it was incredible tennis. I wish I could have played better but if anyone could win this tournament, outside of Venus and me, it's Bianca."
The near-19-year age gap between the two finalists in New York was the largest in open-era tennis, but it was the rookie who rose to the occasion.
Williams started the match with an ace, only to gift the Canadian a break in the opening game with five unforced errors, including successive double-faults.
It was the only break she needed as Andreescu, rock solid on her own serve and with a potent mix of power and spin from the baseline, controlled the first set.
Williams had to fight off five break points in an epic 11-minute seventh game to hold for 3-4.
But another double-fault on set point in the ninth game handed Andreescu a one- set lead after 42 minutes.
Williams was staring down the barrel trailing 5-1 and match point in the second set before nerves took hold of her young rival.
Andreescu lost four games straight to allow Williams back on level terms at 5-5.
But, not to be denied, the teenage sensation finally prevailed on her third match point with a scorching forehand return winner after one hour and 40 minutes.
Andreescu pocketed a cheque for $6 million more than doubling her career on-court earnings and will jump from 15th to world No.5 when the rankings are updated.