Williams next faces No.13 seed Kirsten Flipkens, who beat Dutch qualifier Kiki Bertens 7-5, 3-6, 6-2.
Flipkens leveled the match with a break in the 10th game of the second frame, and once the 13th-seeded Belgian had forced the third set it was Williams who couldn't keep pace.
Williams suffered her earliest French Open exit in 12 years in May, when she crashed to a first-round defeat to Poland's Urszula Radwanska.
Sharapova and Flipkens will be replaced in the 28-player draw by world number 46 Daniela Hantuchova and Christina McHale, who is ranked 79th.
Marion Bartoli revealed a pre-match nap in the locker room was the secret of her success as the French 15th seed raced into the Wimbledon final with a 6-1, 6-2 demolition of Belgium's Kirsten Flipkens on Thursday.
Marion Bartoli wasted little time in advancing to her second Wimbledon final, dancing and grunting her way to a 6-1, 6-2 victory over Kirsten Flipkens on Thursday.
Bartoli, the 28-year-old 15th seed, reached her third career Grand Slam semi-final -- and second at Wimbledon -- with a 6-4, 7-5 win over 20-year-old American, Sloane Stephens on Tuesday.
Fittingly for a tournament shaped by upsets, Flipkens' clash with Bartoli, who was beaten by Venus Williams in the 2007 Wimbledon final, is one of two surprising last four match-ups.
The 27-year-old, a close friend of fellow Belgian and former Grand Slam champion Kim Clijsters, wore down the more powerful Kvitova in two hours and five minutes of attritional tennis under the Centre Court roof.
In the round of 16 she'll face Poland's Urszula Radwanska, a 6-0, 7-6 (7/4) winner over American Jamie Hampton.
Rising star Kei Nishikori said on Thursday he needed to emulate US Open champion Andy Murray's new aggressive style of play if he is to challenge the top players in the men's game.
Thousands of people lined the streets in gloomy Scottish weather on Sunday to give Andy Murray a rousing welcome to his hometown of Dunblane as he celebrated his Olympic and U.S. Open victories.
Andy Murray's five-set victory over Novak Djokovic in the U.S. Open final was watched by more than 16 million on TV, an increase from last year's 11.8 million and the highest total since 2007.
British leaders, tennis chiefs and former players on Tuesday hailed Andy Murray's grit after the Scot became the first British man to win a Grand Slam since 1936.
Andy Murray's Grand Slam breakthrough title at the US Open on Monday has secured the Scotsman's spot among the "Big Four" in this men's tennis era, according to the man he dethroned as champion.
British newspapers hailed Andy Murray's historic achievement in the US Open final on Monday as he ended a 76-year wait for a British men's Grand Slam champion by beating Novak Djokovic.
Andy Murray may have captured the US Open and Olympic titles, but he insisted Tuesday that Roger Federer and vanquished New York rival Novak Djokovic remain the standout players of 2012.