Errani, the 21st-seeded Italian, advanced to her first grand slam final after overcoming a poor second set for a 7-5, 1-6, 6-3 victory over Samantha Stosur, the No 6 seed. The US Open champion hardly looked like the savvy veteran as this match came down the stretch.
Stosur committed 48 unforced errors - 27 more than Errani - in a match that shifted between sunny to windy to cloudy after starting more than an hour late because of rain.
After the win - her first in six tries against Stosur - Errani dropped her racket and fell to her back and on to the damp clay.
A few moments later, she stood up and covered her head with her hands as she looked up to her player guest box, where there was a joyous mix of smiles and tears.
"It's incredible for me," Errani said. "I didn't expect it, and I'm here. So, I don't know what to say."
The victory gives Errani not one, but two dates in the French Open finals. Errani is also teaming with Roberta Vinci in doubles, and they will play Maria Kirilenko and Nadia Petrova for that title.
Errani is the first woman since Kim Clijsters in 2003 to make the finals of both singles and doubles at the French Open. She has a chance to become the first woman to win both since Mary Pierce in 2000.
Errani stands only 1.65 metres and does not pound the ball by any means. But her style is working this year. Entering Roland Garros, she was 0-28 against opponents in the top 10.
Now, she has back-to-back wins against the No 10 Angelique Kerber and the No 6 Stosur, along with victories over past French Open champions Ana Ivanovic and Svetlana Kuznetsova. Which means Errani, too, will reach the top 10 when the next rankings come out.
"Maybe my problem always was that I couldn't believe too much to win with the strong players," she said. But now I beat three in a row. I'm in the final in a grand slam. So I have to maybe try to think a bit different.
Sharapova will reclaim the No 1 ranking following her 6-3, 6-3 victory over Kvitova 6-3, 6-3, which took her to within one victory of completing a career Grand Slam.
"It's an amazing feeling to be in my first [French Open] final. I have been in two semi-finals but it was always my dream of getting to the final stage," she said.
"That's pretty special. After my shoulder surgery, my ranking was out of the 100 in the world, but I thought if I could be No 1 in the world before that then I could do it again."
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