NEW YORK (AFP) — American teenager Coco Gauff came from behind to win the US Open on Saturday, clinching her first Grand Slam title with a battling win over Aryna Sabalenka of Belarus.

Gauff, 19, produced a gutsy performance on the Arthur Ashe Stadium court to win 2-6, 6-3, 6-2 in 2hr 6min to complete a fairytale transformation in her season's fortunes.

The sixth seed from Florida had gone into the final as the underdog against the hard-hitting second seed Sabalenka, who will become world No. 1 in next week's rankings.

But with both players making a slew of mistakes throughout an error-strewn final watched by a star-studded record crowd of 28,143 it was Gauff who held her nerve when it mattered to seal a deserved victory.

The win completed a remarkable turnaround for Gauff, who was left distraught after a first-round exit at Wimbledon in July.

However, she bounced back to win titles in Washington and Cincinnati and has now landed the biggest win of her career, after a shattering loss in her first Grand Slam final at the French Open last year.

"It means so much to me," an elated Gauff said afterwards.

"I feel like I'm a little bit in shock in this moment."

"That French Open loss (last year) was a heartbreak for me. This makes this moment even sweeter than I could imagine."

Gauff, the third American teenager to win the US Open after Tracy Austin and Serena Williams, also used her victory speech to thank those who doubted her talent.

"Honestly thank you to the people who didn't believe in me," she joked.

"To those who thought they were putting water on my fire, they were putting gas on my fire and I'm burning so bright right now."

Sabalenka, meanwhile, blamed self-inflicted errors for her defeat, saying at times she was playing "me against me."