Just three months ago, 18-year-old Emma Raducanu made her tour-level main-draw debut in Nottingham. Today, she is the US Open champion.

The British teenager defeated 19-year-old Leylah Fernandez of Canada 6-4, 6-3 in an all-teenage US Open final to win her first Grand Slam title and her first tour-level title overall.

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Raducanu had a perfect three weeks in New York. She made it through three rounds of qualifying without the loss of a set, then was equally pristine in her US Open main-draw debut, where she also did not drop a set in seven matches.

She is the first woman to win the US Open without dropping a set since Serena Williams in 2014. Raducanu is also the youngest Grand Slam champion since Maria Sharapova won 2004 Wimbledon aged 17.

Ranked World No.150, Raducanu is the lowest-ranked player to win the US Open title since an unranked Kim Clijsters earned the first major of her comeback in Flushing Meadows in 2009. Raducanu is projected to rocket to World No.23 in Monday's new rankings.

Raducanu also makes history by becoming the first qualifier to win a Grand Slam singles title (she had already become the first qualifier to make a Grand Slam final on Thursday).

She is also the first British woman to win a Grand Slam singles title in over 40 years. (Virginia Wade triumphed on home soil at Wimbledon 1977, the year of the Silver Jubilee of Queen Elizabeth II.)

Wade is the only other British woman to reach a US Open final in the Open Era, when the she won the first of her three Grand Slam singles titles in New York in 1968.

"It's an absolute dream," Raducanu said in her victory press conference. "You just have visions of yourself going up to the box, hugging everyone, celebrating. That's something that you always think of, you always work for.

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"With each match and tournament and week, I think I've really built in terms of confidence, in terms of my game, in terms of my ball striking. Everything came together today. I think to pull off some of the shots I did in the big moments when I really needed it was just an accumulation of everything I've learnt in the past five weeks.

"I think what I did very well this tournament was press in the moments that I really needed to. I guess that's why I didn't drop a set on  paper, even though all of the matches were extremely challenging."

Looking back on the ace that won her championship point, Raducanu said, "I don't think I made one serve that wide in the whole match, to be honest. I was like, 'If I'm going to make it, this is going to be the time.' I literally drove my legs up to that ball toss like never before. I landed it. Just disbelief, trying to take everything in, all the moment.

"I think the biggest thing that you have visions of is, for me it was just winning, the winning moment, and going to celebrate with your team in the box, trying to find your way up to the box, just seeing them after the match. That's been playing in my head, like, a couple nights. I've fallen asleep to that."

As she had in all of her previous matches in New York, Raducanu eased through two sets with a mix of power and precision that belies her lack of experience at this level. Against World No.73 Fernandez, Raducanu had 22 winners to Fernandez's 18, while firing one fewer unforced error than the Canadian.

Fernandez continued to use her tremendous footspeed and timing to extend rallies past their breaking points and grit out games other players might not have, and she saved 14 of the 18 break points she faced in the affair.

However, Fernandez got fewer looks on Raducanu's serve, only breaking the Brit twice. Raducanu won 67 percent of points behind her first-service, while Fernandez took only 56 percent of points on her own first delivery in the 1-hour and 51-minute match.

The match was competitive from the get-go, with both players firing rockets at the lines. Raducanu took the early lead after grinding out a break for 2-0 on her sixth break point of that game. However, any thoughts of a runaway were dispelled when Fernandez broke back on her fourth break point of the next game.

There were no more break points until 5-4, where Raducanu fired a backhand crosscourt winner to line up double set point. Fernandez fended off that pair, as well as a third, but on the fourth chance of another lengthy game, Raducanu slammed a forehand winner to notch the one-set lead.

Fernandez, though, grabbed the early advantage in the second set. After a tough hold for 1-1 from 0-40 down, Fernandez used her lefty forehand to set up three break points in the next game, and she attained the break for 2-1. But a backhand crosscourt return winner gave Raducanu the break back immediately, and the Brit started to edge toward victory.

A forehand passing winner gave Raducanu another break as she moved to a commanding 5-2 lead, and in that game she held two championship points. Fernandez again showed off her mettle, saving both and holding for 5-3, and she garnered a break point in the next game after a stunning rally which left Raducanu careening across the court, scraping her knee in the process.

After a short medical time-out to attend to her cut, Raducanu came back to save that break point, and a second, before clinching a third championship point after a long miscue by Fernandez. The third time was the charm, with an ace, and Raducanu collapsed to the court as the newest, and arguably most unexpected, Grand Slam champion.