Austria's Tamira Paszek saved two match points to send Wozniacki crashing out 5-7, 7-6 (7/4), 6-4 in the first round.
Six-time champion Roger Federer reached the Wimbledon third round with a 6-1, 6-3, 6-2 win over Italy's Fabio Fognini, a regal performance witnessed by Britain's Prince Charles.
Prince Charles was on a first visit to Wimbledon in more than 40 years and watched Federer's match with wife Camilla from the royal box.
Camilla, who arrived before Prince Charles at the All England Club, met and chatted with Andy Roddick.
US Open champion Samantha Stosur suffered another Wimbledon nightmare as the Australian fifth seed crashed out in the second round.
Heather Watson ended Britain's 10-year wait to have a woman in the third round at Wimbledon as the youngster swept to a 6-1, 6-4 victory over Jamie Hampton of the United States.
Sara Errani needed only seven seconds on Wednesday to complete a rain-interrupted win at Wimbledon, and she didn't even have to hit a ball.
Errani led American CoCo Vandeweghe 6-1, 5-3 and held the advantage one point from victory when their match was halted on Tuesday evening. Vandeweghe double-faulted into the net on the first point.
Big-serving German Sabine Lisicki edged past Bojana Jovanovski 3-6, 6-2, 8-6 in a hard fought match.
Lisicki made an official complaint over the consistent grunting of her Wimbledon opponent Jovanovski. The German said, "You usually hear the sound of the ball, but I couldn't really hear it because of her grunting."