Sofia Kenin defeated Petra Kvitova 6-4, 7-5 to reach the French Open final on Thursday and will attempt to capture a second Grand Slam of the year following her Australian Open triumph.
Fourth seed Kenin will meet 19-year-old Iga Swiatek of Poland in Saturday's title decider after denying two-time Wimbledon champion Kvitova in her bid for a third major.
Swiatek became the first Polish woman in 81 years to reach the Roland Garros final as she demolished Argentine qualifier Nadia Podoroska 6-2, 6-1.
"I knew I had to be at my best. I am super happy and proud of myself," said Kenin.
The American faltered when serving for the match at 5-4 but broke Kvitova in the following game before closing out the victory over the Czech seventh seed.
Kenin, 21, will try to become the first woman to win two Slams in the same season since Angelique Kerber claimed the Australian and US Open titles in 2016.
"I have won in Australia and had really tough matches this week so that gives me confidence," said Kenin.
"I am going to enjoy this moment and then start to prepare for the final tomorrow."
Before this season, Kenin had never gone as far as the quarter-finals on clay. She lost her only match on the surface this year prior to Roland Garros, 6-0, 6-0 to Victoria Azarenka in Rome.
Kenin, who was taken to three sets in four of her five matches leading up to the semi-finals here, surged 4-1 ahead in the first set against Kvitova with a double break.
The Czech immediately clawed one back and created another opening to level on serve, but Kenin held steady and wrapped up the set when Kvitova smacked a backhand long.
Kenin again struck with a break in game five of the second set, fending off four break points in the ensuing game to keep Kvitova at arm's length.
Her frustration was clear as she blew her first chance to secure victory, but the tenacious Kenin earned a second opportunity and sealed her spot in the final with a gritty service hold.
The championship match will be the first at the majors to feature two players aged 21 or under since Maria Sharapova beat fellow 20-year-old Ana Ivanovic at the 2008 Australian Open.
Great Polish hope
The 54th-ranked Swiatek has yet to drop a set at the tournament, conceding just 23 games through six matches.
The last woman to capture the French Open title without losing a set was Justine Henin in 2007.
"It seems unreal," said Swiatek. "I never thought at the start I would play so good here but I always knew that if I was going to be in the final of a Grand Slam it would be at the French Open."
"It's amazing for me," she added. "It's a dream come true."
Swiatek has matched the run of compatriot Jadwiga Jedrzejowska who finished runner-up at Roland Garros in 1939.
She is only the second Polish woman to reach a Grand Slam final in the Open era after Agnieszka Radwanska at Wimbledon in 2012.
Swiatek becomes the seventh unseeded women's finalist at Roland Garros. Of the previous six, only Jelena Ostapenko in 2017 went on to lift the trophy.
"Basically I wanted to play this match as if it was the first round. I didn't want to think I was in the semi-finals because it would stress me," said Swiatek.
She has not faced Kenin at tour level but defeated her in straight sets in the girls' singles at Roland Garros in 2016.
"I will need to be on a different level, the higher level, even though I'm winning easily right now," added Swiatek.
"Really I have no expectations. I don't care if I'm going to lose or win. I'm going to just play my best tennis."
World number 131 Podoroska was the lowest-ranked semi-finalist in Paris in the modern era, and the first women's qualifier to reach the last four of the French Open.
She will rise to a career a best of 48th after the tournament, having arrived without a single Grand Slam main draw win to her name.
"Of course my ranking is going to change, and the tournaments that I'm going to play. But not my life," said Podoroska.
"I'm going to be the same person. I'm going to try to improve my game, like I've been doing the past few years."