Three champions and a WTA legend make up the Player of the Month ballot for August, but only one can earn your votes and win.
Have a look at the nominees and cast your vote before Thursday at 11:59 p.m. ET! The winner will be announced Friday, September 14.
August 2018 WTA Player of the Month Finalists
Simona Halep: Halep claimed another title in Montreal at the Coupe Rogers near the start of the US Open Series, as the World No. 1 added a third title to her trophy case this season.
"This week, it's been an amazing effort," Halep said during her press conference, following the trophy presentation. "It's brutal, the effort for me. This week it was really tough."
The rematch of the 2018 Roland Garros final between two of the reigning Grand Slam champions lived up to expectations, as Roland Garros winner Halep fended off four set points to claim the opening set, before emerging victorious over 2017 US Open champion Stephens in a tense final set after two hours and 41 minutes of play.
The World No.1 also reached the final in Cincinnati, where she defeated Ajla Tomljanovic, Ashleigh Barty, Lesia Tsurenko and Aryna Sabalenka en route, before falling to another player on the ballot this month.
Kiki Bertens: Bertens claimed the biggest title of her career at the Western & Southern Open in August, saving a championship point to overcome Halep, 2-6, 7-6(6), 6-2 to win her first-ever title off of clay courts at the Premier 5 event.
"I think I didn't have really a good time to get nervous, because I was just so tired," Bertens said after the match. "I think it was such a tough match, and after winning that second set I knew, like, anything is still possible."
Bertens added a second title to her trophy case with the win, having also triumphed at the Volvo Caro Open in Charleston in the spring.
"I had a chat with [coach] Raemon [Sluiter] at 2-1 [in the third set] and I was, like, 'I'm dead,'" Bertens admitted. "Then I said to myself, 'No, I can do this. Let's go for it.'"
"I was, like, 'Yeah, I know this feeling.' I had this feeling before in the practices. So I know that I can keep on going. It's for a title, so of course you can always give a little extra and just go for it. And that's what I did."
Over the course of the week, Bertens scored three other Top 10 wins over Caroline Wozniacki, Elina Svitolina and Petra Kvitova.
Previously in the month, she scored a pair of Top 10 wins, over Kvitova and Karolina Pliskova, en route to reaching the quarterfinals in Montreal.
Serena Williams: Williams reached her second Grand Slam final of a comeback season in New York, scoring statement victories over her sister Venus, 2016 finalist Karolina Pliskova, and US Open upset artist Anastasija Sevasotva along the way.
She lost just one set in six matches prior to being defeated by Osaka in Saturday's championship match, but the 23-time major winner's showing in New York put her firmly back inside the Top 20 of the WTA rankings in her comeback season so far.
Naomi Osaka: One of the WTA's rising stars announced herself in a big way on the biggest stage in August.
Osaka claimed her first Grand Slam title at the US Open, as the BNP Paribas Open champion added another of the sport's biggest trophies to her mantle.
The 20-year-old powered her way through the fortnight with the loss of just one set, culminating with a victory over her idol and 23-time major champion Serena Williams in the final.
Over the course of the fortnight, Osaka defeated Laura Siegemund, Julia Glushko, Aliaksandra Sasnovich, Aryna Sabalenka, Lesia Tsurenko and 2017 US Open runner-up Madison Keys to claim her place in the showpiece match.
Champions Corner: Osaka sets sights on Singapore debut
She became the first player, male or female, from Japan to win a Grand Slam singles title, and soared into the Top 10 of both the WTA rankings and the Porsche Race to Singapore as a result of her victory.
Who is your Player of the Month for August? Vote now!