American teenage sensation Coco Gauff has became the youngest player to win a WTA title in 15 years by beating former French Open champion Jelena Ostapenko in the Linz Open final.

The 15-year-old Gauff, who started the season ranked well outside the world’s top 600, beat Latvia’s Ostapenko 6-3 1-6 6-2 in a topsy-turvy contest on Sunday.

She becomes the youngest WTA singles title holder since Nicole Vaidisova of the Czech Republic claimed her maiden crown in Tashkent at the age of 15 in 2004.

“I’m still overwhelmed and shocked,” Gauff told reporters.

“I guess it’s crazy to say it’s my first WTA title.

“This was definitely not on the calendar at the beginning of the year, because I didn’t think I’d have a chance to get in, and now I’m the champion, so it’s crazy.

“My dad told me when I got in, before the first main-draw match ‘You can’t lose twice in the same tournament!’ I’m sure he never thought it would come this far, to being the champion, but I guess he was right.”

Gauff raced to a 5-0 lead in the final set before Ostapenko rediscovered her rhythm to save two match points and hold on for 5-1.

Ostapenko went on to break Gauff at love to make it 5-2 but the American held her nerve to seal victory on her third match point.

It concludes a remarkable week for Gauff, who went from failing to win her qualifier to entering the main draw as a lucky loser.

Gauff made her opportunity count by beating Stefanie Vogele, Kateryna Kozlova, top seed Kiki Bertens and Andrea Petkovic to reach the final.

Gauff, whose popularity soared at Wimbledon when she beat Venus Williams on her way to the fourth round, is projected to move inside the top 75 in the WTA rankings on Monday.