O, Canada.

History is on hold again. Bianca Andreescu, the 19-year-old fighter from the Toronto suburbs outplayed the great Serena Williams, 6-3, 7-5 to end the American’s bid for a record-tying 24th Grand Slam victory to match Margaret Court.

Despite a frenzied second-set rally by Williams, Andreescu became the first Canadian woman to win a Grand Slam event in the open era. The two women hugged at the net after championship point and Andreescu kissed the court, then laid out on her back in celebration.

Andreescu broke down in tears in the interview room, hiding her face for 20 seconds, explaining how many times she has “visualized” beating Williams at the U.S. Open.

“I’ve been dreaming of this moment for the longest time,’’ Andreescu said through tears.

The Mississauga, Ontario, native said she was nervous all day.

“I tried to breathe as much as I could from the moment I woke up, to the match,’’ she said.

The precocious Andreescu praised Williams for her sportsmanship and for saying kind words to her in the locker room, adding, “Who knows? Maybe I can be even better.’’

Williams still has not won a tournament title since she became a mother two years ago. One year after her meltdown during her Open finals loss to Naomi Osaka, Williams stayed relatively composed amid the onslaught, though her facial expressions in the second set grew more dismayed.

“It’s really hard to say ‘You did OK,’ because I don’t believe I did,’’ Williams said. “I believe I could have played better. I believe I could have done more. I believe I could have just been more Serena today. I honestly don’t think Serena showed up. I have to figure out how to get her to show up in Grand Slam finals.

“It’s super frustrating to be so very close … but so far away.”

Nevertheless, Williams still managed to rally brilliantly from 5-1 and two breaks down in the second set to square the match at 5-5 amid a deafening din.

Andreescu admitted she “had some doubts” because she has seen Williams rally from 5-0 before.

“I told myself to stick to my tactics,’’ Andreescu said. “The crowd really helped her as well. I barely could hear myself think. It was really, really loud. I’m sure it’s nice for the Americans to come on that court.”

At 5-5, Andreescu held on with a big service game to go up 6-5 and she then broke Williams with two service winner spiced with renewed shaky play from the American.

“I was fighting at that point to stay out there a little more,’’ Williams said of her comeback. “The fans started cheering so hard it made me play a little bit better and fight a little bit more. If anyone could win this tournament outside of Venus, I’m happy it’s Bianca.”

Andreescu’s serve was consistent and solid. She got in 84 percent of first serves during the first set. Williams’ delivery became erratic with untimely double faults (eight total) and she played too many backhands into the doubles alley. At 37, she looked to not have enough stamina for a second-set comeback against a player 18 years her junior.

Andreescu, who won at Indian Wells and Toronto in a sensational 2019 jump, is 7-0 against top 10 players this year, and she is known on the tour as a premier fighter. During last year’s Open, Andreescu was in qualifiers and didn’t advance to the main draw.

This was the fourth final which Williams has made since winning her 23rd Grand Slam, but she has been unable to pull off her attempt to tie Court for the all-time record. She’ll get another crack at it at the Australian Open in January in Court’s home country.

The fans were cheering madly for the icon from Compton, Calif., only to be disappointed. It has been a sweet year for Canadian sports with Andreescu winning the Open nearly three months after the Toronto Raptors brought the NBA championship to The North for the first time.

As Andreescu did her post-match interview at ESPN’s outdoor studio, a flock of flag-waving Canadian fans chanted “You the North’’ and the Raptors and Vancouver Canucks tweeted congratulations.

Williams won the player box battle, with Megan Markle (the Duchess of Sussex and a friend of Serena’s), sister Venus Williams, Anna Wintour of Vogue and celebrity coach Patrick Mouratoglou, who didn’t get flagged for coaching this year.

Andreescu’s coach, Sylvain Bruneau, was delighted at the poise in her first Slam Final.

“She was fearless for big parts of the match and impressive how she started the match,” Bruneau said. “Then from 5-1 up to 5-5, the thing slipping away, Serena finding herself, for her to reset, it was really special.’’

Keeping her humor, Andreescu told the crowd after receiving the $3.85 million check: “I know you wanted Serena to win, so I’m so sorry.’’