In Tuesday's opening White Group match, Sharapova - a four-time title winner on the WTA Tour this year - was the architect of her own downfall as she made an astonishing 76 unforced errors across three gruelling sets.
Nevertheless, the world number two was able to remain competitive until Wozniacki eventually reeled off four games in succession to secure a 7-6 (7-4) 6-7 (5-7) 6-2 triumph that took three hours and 13 minutes.
Sharapova was the more aggressive player throughout, but was left to rue a string of mistakes as her Danish opponent gained reward for some superb defensive play.
"I'm feeling a little tired," said a smiling Wozniacki after completing her victory.
"It was a great match. It's always tough to play the first one, getting the rhythm, but in the third set I felt like I stepped it up a little bit."
Sharapova demonstrated impressive tenacity to claim a 5-4 lead in the opening set after initially falling 3-0 down.
However, the French Open champion was unable to kick on and, after saving a set point at 5-6, she lost five points in a row to lose a tie-break, with her ninth double-fault handing Wozniacki a one-set lead.
Sharapova was broken at the beginning of set two, but then received a lifeline as Wozniacki - apparently distracted by the overhead lighting in the Singapore Sports Hub - gave up serve in game six.
The inconsistent Sharapova sent a forehand wide in the next game to lose serve for a fourth time, only to respond once again by preventing Wozniacki from serving out the match at 5-4.
A thrilling 12th game saw Wozniacki save a set point, the result of a wide forehand from Sharapova at deuce being called in with her opponent out of challenges, to force a second tie-break.
Sharapova was the victor on this occasion, winning 7-5 following a flurry of mini-breaks to set up a decider after more than two and a half hours on court.
After two lengthy sets, the third proved more one-sided.
Wozniacki gave up another early break to allow her Russian rival to level at 2-2, but the eighth seed then strung together four straight games and it was fitting that the match was rounded off by yet another unforced error from Sharapova.