Reigning champion and world No. 1 Iga Swiatek swept into the French Open final on Thursday after unheralded Karolina Muchova saved a match point before stunning second seed Aryna Sabalenka.

Swiatek defeated Brazil's Beatriz Haddad Maia 6-2, 7-6 (9/7) and will face the 43rd-ranked Muchova from the Czech Republic on Saturday as she targets a third Roland Garros title in four years.

The 22-year-old Pole, who improved her record in Paris to 27-2, is bidding to become the first woman to successfully defend the title since Justine Henin in 2007.

She is also the youngest woman to reach three French Open finals since Monica Seles at the start of the 1990s.

"It's really amazing. Honestly, it's tough to play such a long tournament and I'm pretty happy I am able to play consistently and every year have a good result here, and I am pretty excited for Saturday," Swiatek said.

Haddad Maia, the first Brazilian woman to reach a Grand Slam semi-final since seven-time major winner Maria Bueno in 1968, broke Swiatek to love in the opening game but the top seed soon took charge.

Swiatek won five of the next six games before breaking Haddad Maia for a third time to close out the set.

Haddad Maia clawed out a 3-1 lead in the second set but Swiatek pocketed the next three games.

She fended off three break points at 4-all and saved a set point in the tie-break before halting the run of the 27-year-old left-hander who had never got past the second round of a Grand Slam before this French Open.

"It wasn't easy, she's a fighter and she showed that," Swiatek said.

"I knew I had to be ready for every game and that the momentum could change really quickly and that's why I played so well in the tie-breaker."

Muchova will play her first Grand Slam final after overturning a 5-2 deficit in the final set to knock out Australian Open champion Sabalenka and snap her 12-match winning run at majors.