French Open champion Li Na's title defence ended on Monday when she was knocked out in a flurry of errors by Kazakh qualifier Yaroslava Shvedova 3-6 6-2 6-0.
After taking the first set, the Chinese seventh seed collapsed, taking only two games out of the next 14.
Last year's champion made 41 unforced errors as she spectacularly lost control of a match in which she had looked to be cruising towards victory.
The blustery conditions on Court Suzanne Lenglen made serving difficult, but the Kazakh's aggressive approach left Li flat-footed.
Her rhythm went to pieces in the face of an all-out assault from the doubles specialist who was not expected to be a realistic challenger in the singles draw, even in a tournament jam-packed full of shock results.
Shvedova, who has won grand slam doubles titles at both Wimbledon and the US Open in 2010, had signalled her intent coming into the match having not dropped a set in her opening three matches.
Having stormed through the second set, Shvedova broke her opponent's serve three times in the decider, and while she wasted two match points in the final game, she eventually closed it out when Li netted a tame backhand.
Shvedova, ranked 142 in the world in singles, will now play the winner of Varvara Lepchenko's match against Wimbledon winner Petra Kvitova in the quarter-final.