The French Open champion will be a first-time major victor while victory will also crown the Romanian third seed as the new world number one, replacing Angelique Kerber.
A year after losing in the first round at Roland Garros, the 17th-seeded Schiavone became the first woman from Italy to reach a Grand Slam final - and then won the title, too, shortly before turning 30.
"To be in the final again is great".
When Serena Williams announced she was pregnant and when Maria Sharapova was not given a wild card into the French Open, it didn't take a genius to suggest that Simona Halep, the 2014 runner-up, would be the most likely to take the trophy.
Mixed in with her scintillating winners, including forehands faster than anything men's world number one Andy Murray has managed here so far, were 45 unforced errors, some of which could have embellished a video nasty.
In contrast, Halep registered 14 in both columns.
She was more focused in the second set, forcing Halep to hit a backhand wide to break for 4-2, then holding for 5-2 after saving three break points.
Romania's Simona Halep celebrates as she defeats Karolina Pliskova of the Czech Republic during their semifinal match of the French Open tennis tournament at the Roland Garros stadium, Thursday, June 8, 2017 in Paris.
In the end, she could at least reflect on progress in Paris - before this year, she had never got beyond the second round in five attempts.
The 25-year-old has since dismissed concerns over her fitness and finds herself one win away from a memorable maiden Slam title triumph that would also see her supplant Angelique Kerber at the top.
"I was like, 'There is no chance I make final here, '" she said.
Ostapenko, though, produced the required resolve when play resumed, with a double break putting her on the brink of victory, which she delivered when holding her serve to love for a 4-6 6-2 6-2 win over the 11th seed in just under two hours on court.
"It was a really tough match". I think that's what made the difference.
Halep could have won the first set easier if she had converted break points in the fifth and ninth game.
"I felt a little bit tight because.I was very close to making the final and some thoughts were in my mind", added Ostapenko, whose previous best run at a Slam was reaching the third round at the Australian Open. "I was already in the semis, and I was just trying to enjoy the game and show my best".
"If I could be only disappointed on one aspect of the match it's some opportunities I had in the first set", Bacsinszky said. "I'm just happy with the way I celebrated my birthday".
Pliskova, who is not a claycourt expert, played her best match of the tournament, but it was not enough to subdue Halep, whose never-say-die attitude helped her survive a quarter-final against Elina Svitolina, during which she saved a match point.
She hits more winners than anyone.