US tennis player Sofia Kenin fought back from a set down against Spaniard Garbine Muguruza to win her first Grand Slam title at the Australian Open with a 4-6, 6-2, 6-2 win on Saturday.

The 21-year-old Kenin, seeded 14th at the tournament, converted her second match point against the two-time Grand Slam champion, who double-faulted on the final point, to end an engrossing contest that lasted for more than two hours.

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Both women produced a fitting and intense final that was played under a closed roof at Rod Laver Arena after a rainy day in Melbourne.

After dropping the first set, the Moscow-born Kenin played some outstanding defence and put increasing pressure on her opponent's serve to level the match, forcing a deciding third set.

Kenin won the last four games of the match, breaking the former world number one for 4-2, before sealing the win, as Muguruza hit three more double faults in the final game.

"This is my first speech, but I'm going to try my best," Kenin said during the trophy ceremony at Rod Laver Arena, where the retractable roof was shut because of rain much of the day.

"My dream has officially come true," she told the crowd. "Dreams come true. So if you have a dream, go for it, and it's going to come true."

With the win, Kenin became the youngest to win the Australian Open since Maria Sharapova defeated Ana Ivanovic in 2008 when they were both aged 20.

In the men's final, defending champion Novak Djokovic will be looking to clinch a record eighth title and 17th overall major trophy when he faces Austrian youngster Dominic Thiem on Sunday.