Mika Stojsavljevic became the first British girls' Grand Slam champion in 15 years after defeating Japanese No.7 seed Wakana Sonobe 6-4, 6-4 in the US Open junior final. Meanwhile, Morocco's Malak El Allami and Norway's Emily Sartz-Lunde claimed the girls' doubles crown, becoming the first ever girls' major titlists from their respective countries.

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The unseeded Stojsavljevic follows in the footsteps of Heather Watson, who was the US Open girls' winner in 2009. The 15-year-old Londoner was previously the Wimbledon junior doubles runner-up in July alongside compatriot Mingge Xu, who had fallen to Sonobe in the semifinals this week.

Stojsavljevic's run to the title included two major upsets. In the third round, she took out Australian No.1 seed Emerson Jones 7-5, 6-4; and in the semifinals she overpowered American No.3 seed Iva Jovic 6-0, 3-6, 6-3. The previous week, 16-year-old Jovic had delivered an eye-catching performance as a wild card in the women's main draw, upsetting Magda Linette in the first round before stretching No.29 seed Ekaterina Alexandrova to three sets.

The final was a rematch of two junior Slam first-round ties last year, at Wimbledon and the US Open, both won by Stojsavljevic from a set down. In a clash of first-strike power, it was Stojsavljevic who kept a cleaner scorecard, striking 14 winners to Sonobe's 13 and committing 25 unforced errors to her opponent's 30.

Sonobe, 16, had not dropped a set en route to the final, and seemed to settle first, saving break point to hold for 3-2 after an edgy start for both. But Stojsavljevic responded by winning six of the next seven games to go up 2-0 in the second set -- a dominant passage of play that gave the Briton a decisive lead.

2024 US Open girls' finalist Wakana Sonobe.

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Stojsavljevic also showcased some useful variety in the second set, winning six out of seven points at net overall. Her backhand proved her most reliable weapon, though, sealing the first set with a crosscourt winner and tallying another two clean winners from that wing as she served out the match to love.

Stojsavljevic and Sonobe have both begun to make inroads into the pro game already as well, and are ranked No.641 and No.792 respectively on the PIF WTA Rankings. Stojsavljevic captured her first pro title at the Nottingham ITF W35 in April, defeating former No.26 Tamira Paszek en route. She went on to make her WTA qualifying debut in Birmingham, falling 6-2, 6-3 to Camila Osorio.

Sonobe has already made three ITF W15 finals to date and made her WTA qualifying debut as a wild card in Abu Dhabi this February, falling 6-4, 6-0 to Bernarda Pera.

El Allami, Sartz-Lunde make history for Morocco, Norway

The unseeded duo of El Allami and Sartz-Lunde had already made history for their respective countries by reaching the final this week. No girl from either Morocco or Norway had ever contested a junior Grand Slam title match. The 18-year-olds didn't stop there, though, triumphing 6-2, 4-6, [10-6] over Czech-German pair Julie Pastikova and Julia Stusek to lift the trophy.

It was the third match El Allami and Sartz-Lunde had sealed in a super-tiebreak this week -- and in the previous two, they had defeated both of the singles finalists. In the first round, they edged No.3 seeds Sonobe and Alena Kovackova 6-2, 2-6, [10-7], and in the quarterfinals took out No.5 seeds Stojsavljevic and Xu 7-5, 2-6, [10-8].

2024 US Open girls' doubles champions Emily Sartz-Lunde and Malak El Allami.

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El Allami, the younger sister of former Top 500 pro Fatima-Zahrae, made her WTA main-draw debut at Rabat 2023 on home soil and impressed in a first-round loss to Kamilla Rakhimova. That year, she also made history by becoming the first Moroccan girl to win a match at junior Wimbledon.

The title marks a victorious culmination to the junior careers of El Allami and Sartz-Lunde, who will both imminently head down the college tennis path. El Allami moved to New York a week ago to begin her freshman year at Columbia University, while Sartz-Lunde will start at the University of Michigan this year.