International, this time losing to Petra Kvitová. During the event, she defeated three top 15 players, including Simona Halep for her first career victory over a current world No. 1 player. At her next tournament, Barty made her first Grand Slam quarterfinal at the Australian Open, defeating Maria Sharapova before again losing to Kvitová, becoming the first Australian to make the quarterfinals at the event since Jelena Dokic in 2009. After a fourth round appearance at the Indian Wells Open, Barty won the Miami Open for her first Premier Mandatory title. She defeated three top-10 players in the event, including No. 2 Kvitová in the quarterfinals and No. 7 Karolína Plíšková in the final. With this result, she also made her top-10 debut. In the lead-up to the French Open, Barty played only two clay court events. Her best result was a quarterfinal at the Madrid Open, where she lost to Halep. She closed out the clay court season by winning her first Grand Slam singles title at the French Open, defeating Markéta Vondroušová in the final, dropping just four games. With the title, Barty became the first Australian to win the French Open in singles since Margaret Court in 1973 and the first Australian to win a Grand Slam singles title since Sam Stosur at the 2011 US Open. She also rose to No. 2 in the world. Barty then followed up this title with another at her next event, the Birmingham Classic, to become the No. 1 ranked player in the world. She was the second Australian to be No. 1 in the WTA singles rankings after Evonne Goolagong Cawley. Barty's win streak came to an end at 15 matches when she was defeated at Wimbledon by Alison Riske in the fourth round. Barty lost the No. 1 ranking to Naomi Osaka in early August after an opening round loss at the Canadian Open. The following week, she fared better at the Cincinnati Open, falling to Svetlana Kuznetsova in the semifinals. At the US Open, she was upset in the fourth round for the second time in a row at a Grand Slam tournament, this time to Wang Qiang. Nonetheless, she regained the No. 1 ranking, and rebounded during the Asian hard court season. She reached another semifinal at the Wuhan Open followed by a runner-up finish to Osaka at the China Open. At the end of the