As shared by the tournament's official Twitter account, it was sweet revenge for the Chinese player:
It wasn't the only upset of the day, as defending champion Jelena Ostapenko lost to Kateryna Kozlova.
Earlier in the day, Grigor Dimitrov advanced to the next round with a straight-sets win over Mohamed Safwat. For Sunday's full results, click here.
Here are some selected results:
Qiang Wang def. (9) Venus Williams: 6-4, 7-5
(4) Elina Svitolina def. Ajla Tomljanovic: 7-5, 6-3
(10) Sloane Stephens def. (LL) Arantxa Rus: 6-2, 6-0
Kateryna Kozlova def. (5) Jelena Ostapenko: 7-5, 6-3
(19) Kei Nishikori def. (WC) Maxime Janvier: 7-6 (0), 6-4, 6-3
(4) Grigor Dimitrov def. (LL) Mohamed Safwat: 6-1, 6-4, 7-6 (1)
(10) Pablo Carreno Busta def. (Q) Jozef Kovalik: 4-6, 6-1, 7-5, 7-6 (5)
The 2018 season has so far been one to forget for Williams, and at the age of 37, one has to wonder what the former world No. 1 has left in the tank.
As shared by Ben Rothenberg of the New York Times, her record in Grand Slams this year has been appalling:
Williams has never been at her best on clay, and Wang was able to negate her raw power in the rallies by keeping the action moving from side to side. Williams ended up with 35 unforced errors, compared to just 14 from her opponent.
Svitolina fared much better in her match against Ajla Tomljanovic, using a solid combination of aggression and raw athleticism to come back from a shaky start.
The 23-year-old completely missed her start but turned things on when needed:
Defending French Open champion Ostapenko made some unfortunate history, becoming the first reigning champion to lose in the first round since 2005, as Christopher Clarey of the New York Times noted:
Meanwhile, Nishikori and Dimitrov both picked up their first wins of the tournament with relative ease in the men's draw, and for the Japanese star, it marked his first Grand Slam victory since Wimbledon of last year.
Wild card Janvier put up some solid resistance in the opening set, but he was swept aside in the tiebreak and lost all momentum.
Dimitrov was supposed to play Viktor Troicki, but the latter pulled out at the last minute, giving lucky loser Safwat a chance. Here are some highlights from their encounter:
Safwat became the first Egyptian to play in the main draw of a Grand Slam in this century and put up a good fight, improving as the match wore on. He couldn't deal with the Bulgarian's physical advantage in key moments, however, and won just a single point in the tiebreak in the final set.