Serena Williams and Bianca Andreescu pose with the second-place and first-place trophies.

Teenager Bianca Andreescu became Canada's first Grand Slam singles champion Saturday with a rollercoaster 6-3, 7-5 win over 23-time major champion Serena Williams in the US Open final.

The 19-year-old Andreescu became the youngest Grand Slam winner since Maria Sharapova at the 2006 US Open, handing Williams a fourth consecutive defeat in the final of a major to again deny her a record-equaling 24th Slam title.

Serena Williams and Bianca Andreescu hug after Andreescu wins the women's singles final.

"It's so hard to explain in words but I'm just beyond grateful and truly blessed. I've worked really, really hard for this moment," said Andreescu, who had won just two Grand Slam matches ahead of her US Open main draw debut.

"This year has been a dream come true. Being able to play on this stage against Serena, a true legend of the sport, is amazing.

Meghan Markle, Duchess of Sussex and Serenas mother Oracene Price look on after Serena Williams lost to Bianca Andreescu.

Generous Serena

Andreescu, who wasn't even born when Williams won her maiden Slam at the 1999 US Open, responded with a comfortable hold, a pattern that repeated itself until the Canadian threatened to run away with the opening set.

Serving at 2-4, Williams erased five break points with a combination of aces and booming groundstrokes but Andreescu was knocking on the door once more as the American served to stay in the set.

Serena Williams of the United States is interviewed by ESPN Reporter Tom Rinaldi.

A forehand winner earned the youngster a set point, and Williams duly her gifted her the opener with another double fault.

Andreescu had failed to even reach the main draw at Flushing Meadows the past two years, twice falling in the first qualifying round, and her confidence continued to flow as she surged 2-0 ahead in the second -- Williams again doubled-faulting on break point.

Agence France-Presse