Five-time champion Serena Williams suffered her earliest Wimbledon defeat since 2005 as she lost to France's Alize Cornet in the third round.
Cornet, ranked 24th, won 1-6 6-3 6-4 on Court One to claim her second victory of the year over the world number one.
It is only the third time in 15 visits to Wimbledon that Williams has lost so early, and she has not been past the fourth round of a Grand Slam in 2014.
Cornet, 24, had never before beaten a top-20 player at a Grand Slam.
Cornet has only reached the fourth round at a Grand
Slam once before, in Australia five years ago
"I just cannot believe it," she told BBC Sport. "Three years ago I couldn't play on grass, I was so bad, but now I have beaten Serena, the world number one on her own court.
"I have to get used to it and focus on the next match because the tournament is not over for me. I am not sure how I did it but just with the heart and the help from the crowd."
Williams said: "She kept her unforced errors really low. I think I made a few errors too many. She was going for her shots. She played really well today."
Cornet did have a confidence-boosting win over Williams in Dubai earlier this year to call upon, but it still came as a major shock to see her grab the initiative and dominate the closing stages.
Williams, 32, had looked edgy in the opening exchanges, making five errors and two double faults before the rain came at 1-1 to force the players off for several hours.
A run of five straight games on the resumption suggested the American had overcome whatever had been troubling her earlier, but the feisty Cornet came battling back.
After failing to serve out the set at 5-1, she converted at the second attempt and was pushing hard at the start of the third against an uncertain Williams.
Four break points slipped by in the opening game, but Cornet was having plenty of joy on the Williams second serve and moved to within two points of victory on serve at 5-2.
Williams has already lost in the fourth round of the Australian Open and the second round of the French Open this year, and was not about to give up on another chance at an 18th major title.
She heaped the pressure on Cornet with a break of serve, but two games later a wayward forehand and a poor volley gave the Frenchwoman match point, and Williams could only steer a backhand into the net.
Cornet celebrated the win of her career, adding: "It is the biggest shock of the tournament because she is the world number one and I still can't believe I did it, me! I am loving it here in London."
Williams will get her next chance to add to her haul of major titles when she defends her US Open crown in August, but she said the competition was getting tougher.
"It's difficult," said the American. "If I'm not playing a great, great match, these girls when they play me, they play as if they're on the ATP Tour, and then they play other girls completely different.
"It's never easy, you know, being in my shoes. But you've got to be ready."