World number two Ashleigh Barty is out of the US Open after succumbing to a straight sets defeat by Qiang Wang.
The 27-year-old produced one of the performances of her career to stun the Australian with a 6-2, 6-4 triumph in an hour and 27 minutes on court.
Wang, who had never been beyond the third round of a major in 20 attempts, kept Barty back with consistent groundstrokes that landed deep in the court and she had just 14 unforced errors to her opponent's 39.
Barty overcame three match points before Wang finally served out the match, pumping her fist in the air as the Australian's return sailed long.
Barty's loss ends an impressive run of Grand Slam performances this year, having won the French Open, reached the quarter-finals of the Australian Open and the round of 16 of Wimbledon.
That record, along with titles at tour events in Miami and Birmingham, England, helped her hold the No. 1 ranking for nearly two months this summer before Naomi Osaka regained the spot.
Wang is the first Chinese woman to get this far in the US Open since Shuai Peng's run to the semis in 2014.
She will face the winner of the match between 23-time Grand Slam winner Serena Williams and 22nd seed Petra Martic.
Additional reporting from Reuters.
