Williams fell into a 0-40 hole in the fifth game of the second set and Wang delivered a forehand victor to take a 3-2 lead.
Romania's Simona Halep, the 2018 runner-up, endured a nervy time against British qualifier Harriet Dart before sealing a 6-2 6-4 win for the 90th Grand Slam main draw victory of her career.
Djokovic is seeking to become only the third man to win eight or more titles at the same Grand Slam after Rafael Nadal (12 at Roland Garros) and Roger Federer (eight at Wimbledon). Since giving birth to daughter Alexis Olympia later that year, the American legend has gone on to contest seven Slams and reached the final on four occasions, but that 24th major crown remains elusive.
She couldn't escape Qiang Wang, though, who beat Williams (6-4, 6-7, 7-5).
Dellien, the first Bolivian to compete at the Australian Open, had just broken inside the top 250 in the world rankings this time two years ago; two years before that he was just inside the top 500.
Due to rain, Ito's opener was pushed back to Tuesday, but the 31-year-old from Japan needed little time to brush past lucky loser Prajnesh Gunneswaran 6-4 6-2 7-5.
The 33-year-old took to Instagram and shared a photo with the kid named Anita.
"I just made far too many errors to be a professional athlete today", said Williams afterwards.
Wang quickly outperformed these scores and scores on Friday, largely due to an nearly flawless game in the first set. She played a good couple of matches and even registered a win over 2019 champion Ashleigh Barty.
The incident took place during his second-round match at the ongoing Australian Open against Federico Delbonis of Argentina.
Wang, 28, said Chinese New Year celebrations would be on hold before her fourth-round clash against Tunisia's Ons Jabeur, who knocked out Williams's good friend and former world number one Caroline Wozniacki, drawing the curtain on the retiring Dane's career in tennis. He added, "I was so scared for her honestly the ball was so quick and (hit her) straight on the head".
The American admitted she thought she had done the hard work by winning the second set, saying: "I was optimistic I would be able to win".
