Ostapenko is the first teenager to reach a Grand Slam semifinal since Madison Keys at the 2015 Australian Open and the youngest player to reach the last four in Paris since Ana Ivanovic in 2007.
Wozniacki takes first set
It couldn't have been a better start for the Dane as she raced out to a 5-0 lead. After a quick hold, Wozniacki broke Ostapenko to 15, but she didn't have it all her own way on serve as she saved five break points in her next two service games.
The key moments of the match followed as Ostapenko mounted a comeback, reeling off four straight games. She broke on the third time of asking in the seventh game and after saving a pair of set points on her own serve, broke when the former world #1 netted a backhand to pull back the entire deficit.
The Latvian's inexperience showed when she served to stay in the set. Trailing 5-4, Wozniacki broke the teenager to love when Ostapenko sprayed three errors and double-faulted at 0-40 and the former U.S. Open finalist was a set to the good.
Ostapenko dominates second set
After a pair of holds were recorded to start the second set, it was the 19-year old who struck first, breaking for her first lead in the match at 2-1. Wozniacki was able to peg Ostapenko right back, breaking, but the Dane's serve, perhaps her weakest shot, was breached again, a wayward backhand giving Ostapenko a 3-2 lead.
From there, the Latvian put on a clinic, racing through the final three games, her powerful groundstrokes beginning to take its toll on the Dane and after a second break, the match was halted for three hours as the rain began to fall. After coming back from the stoppage, Ostapenko served for the set at 5-2 and she won the last two points from 30-all to level the match at one set apiece.
Ostapenko puts on shotmaking display in final set to reach semifinals
Perhaps the most naturally gifted shotmaker in the game, Ostapenko continued her attack and after a long third game, she found herself with a break point chance, but Wozniacki fought it off to hold. After a second rain delay, this one lasting 30 minutes, she was in trouble in her next service game and this time, was unable to escape as Ostapenko's penetrating game took its toll, a weak forehand by the Dane giving the Latvian a 3-2 lead.
The winners were flying off of Ostapenko's racket on nearly every point, Wozniacki with no answer to her opponent's sensational performance. In the sixth game, Ostapenko blasted a backhand that Wozniacki could barely get her racket on and it was now 4-2. The teen was a game away from the semifinals.
Serving for the match, the Latvian showed sensational poise to close out the Dane. At 40-0, one final forehand ripped crosscourt was met with an errant backhand reply and Ostapenko had sealed her spot in the semifinals against 30th seed Timea Bacsinszky.
Following the match, Ostapenko, who fired 38 winners and improved to 4-0 lifetime against Wozniacki, spoke about a number of topic on her run in Paris: "Every match we played was a very tough match, because she's playing really well, and she's very consistent.
"In my mind, every time I go on court to play against her, I just know that I have to stay aggressive, but to not go for every shot because I have to be consistent, as well. "
About facing Bacsinszky on what is the birthday for both of them:
"Both of us will have the birthday, so I'm really looking forward to the match," said the soon-to-be 20-year old (Bacsinszky will turn 28 on Thursday). "I think maybe this [birthday] is one of the best ones - because to play semifinal of Roland Garros on your birthday, I think it's really nice.
"I actually didn't expect that it would be here in Paris, but I'm really happy it's here."