
Top seed Williams, a five-time Wimbledon champion, had reached at least the last 16 in each of her previous seven visits to the All England Club, but Cornet fought back from a set down to end that sequence in two hours and four minutes of gripping drama on Court One.
It was the shell-shocked 32-year-old’s earliest Wimbledon exit since her loss to Jill Craybas at the same stage in 2005.
Serena could have no complaints about an embarrassing defeat which continued a disappointing campaign for the 17-time Grand Slam champion, who has failed to get beyond the fourth round at any of the three majors so far this year.
After a sluggish start, Cornet produced some simply brilliant play in the final two sets and the reward for the best result of her career is a fourth round clash against Canadian 13th seed Eugenie Bouchard on Monday.
It will be the 24-year-old’s first appearance in the second week of Wimbledon at the eighth attempt and only her second career fourth round appearance at a Grand Slam.
Cornet, who celebrated one of the great Wimbledon upsets by kissing the turf in jubilation, said: “I just can’t believe it. A few years ago I couldn’t even play on grass. I was so bad.
“To beat Serena at Wimbledon, wow, it is just a dream. It is the biggest upset in the tournament because she is the world number one and has won here so many times.
“I thought it was going to be tough when I lost the first set but finally I did it.
“I can’t believe that I did it myself. It is a great moment. I’ve been working so hard and this is the reward.”