Australian Ashleigh Barty will become the new world number one after beating Julia Gorges 6-3 7-5 to win the Nature Valley Classic in Birmingham.

The French Open champion will replace Japan's Naomi Osaka at the top when the rankings are released on Monday.

Barty, 23, will become the first Australian woman since Evonne Goolagong in 1976 to be world number one.

"I'm a little bit speechless at the moment," Barty said during the on-court trophy presentation.

Barty gave up tennis in late 2014 to play cricket before returning to the sport in 2016, winning her first Grand Slam title at Roland Garros earlier this month.

"It's been a whirlwind few weeks for me, a whirlwind year, but to be able to follow in the footsteps of Evonne, even to be mentioned in the same sentence as her, is incredible," she added.

"You always dream of it [being world number one] as a little kid but for it to become a reality is incredible.

"It's not something that was even in my realm, this year we were aiming for top 10 and now to be where we are is a testament to all of the people around me.

"We started from scratch three and a half years ago without a ranking and now to be where we are is not only for me, but a massive, massive achievement for them [the rest of her team]."

The victory over Gorges, with whom she plays doubles and who she described as "one of my best friends on tour", was sealed in just under an hour and a half.

German world number 19 Gorges said it had been a privilege to share the court with her.

"She served an ace when I had set point so I think that says it all," she said. "It was a high-quality match and she deserved to win. I did everything I could today but she was better."