Marta Kostyuk reached the quarterfinals at the French Open for the first time on Sunday by taking out four-time champion Iga Swiatek 7-5, 6-1 and ruining her birthday.
Kostyuk, who is undefeated on clay this season, had lost their three previous matches and never taken a set against the former top-ranked player, who turned 25 on Sunday.
Swiatek's loss guarantees a new French Open singles champion in the men's and women's draws; Novak Djokovic was the last former men's champion standing before he was knocked out in the third round Thursday.
"To beat such an unbelievable player who won four times here, I'd lost [three] times to her, never taken a set off her, I still cannot believe it," Kostyuk said. "I think the most important thing I've been doing is really just trying to enjoy. I woke up this morning and I just thought about what an unbelievable day I have to live today to play on Chatrier against Iga."
Kostyuk defended extremely well Sunday, chasing Swiatek's shots all over the court, and produced some stunning groundstroke winners while her rival was undone by her own mistakes.
"It is harder a bit to handle stress for me in the last year," Swiatek said. "Today I felt off and I did mistakes that I didn't want to do, and I wanted to play safe but the ball flew everywhere."
An intense baseline battle unfolded from the outset, and Swiatek earned the first break when she overwhelmed Kostyuk after a long rally with a backhand winner. Kostyuk broke back immediately, though, only to drop her serve again and hand Swiatek a 5-4 lead.
The Polish player showed signs of nerves as she double-faulted, shanked a forehand wide and missed a volley at the net, allowing Kostyuk to level at 5-5. Swiatek hit two more double faults in the 12th game, and Kostyuk sealed the set with a backhand passing shot.
As Swiatek briefly left the court, Kostyuk kept herself warm by stretching and hopping beside her chair. She received some applause as she did a few dance moves to the music playing in the stadium.
When play resumed, Swiatek broke but yet another double fault coupled with more unforced errors brought her opponent back at 1-1. Kostyuk then won the last five games.
Kostyuk had reached the fourth round at Roland Garros in 2021, losing to Swiatek.
The 15th-ranked Ukrainian is in a strong run of form and extended her winning streak on clay to 16 matches. Ahead of Roland Garros, she won in Madrid -- the biggest title of her career -- after she claimed another clay-court title in Rouen, France.
"The most important thing that I've been doing this whole time is really just trying to enjoy," she said. "It's helping. I want to keep enjoying. I try not to focus at all on winning or losing because I'm not playing tennis to win, I'm playing tennis because I love it."
After her first-round win, Kostyuk fought back tears when she described how she found out on the morning of the match that a missile almost hit her parents' home in Ukraine. She said she was feeling exhausted after speaking out against the war for so long but would continue stating her opinion.
Swiatek has not won a title on clay since the 2024 French Open. This was her earliest exit at Roland Garros since her main draw debut in 2019, when she also lost in round of 16.
Kostyuk will face fellow Ukrainian Elina Svitolina in the quarterfinals. The No. 7 seed posted a comeback 4-6, 6-4, 6-0 win over No. 11 Belinda Bencic.
"There's going to be Ukraine in the semifinals, so it's already amazing," Svitolina said. "I think it couldn't be a better, amazing achievement for Ukrainian tennis. I think in such a difficult situation right now in the war, with the invasion, it's really, really difficult, and I think it's really inspiring for the next generation to really believe that it is possible one day to play on this court and win."
No. 18 Sorana Cirstea also advanced to the quarterfinals with a 6-3, 7-6 (4) win over Wang Xiyu.
Cirstea, 36, is planning to retire at the end of the season. She is the third-oldest woman to reach the round of 16 at the French Open in the Open era (since 1968) and the oldest since Billie Jean King in 1980.
She last reached the quarterfinals at 19 years old in 2009. The gap between Cirstea's first and second Grand Slam quarterfinal appearances in Paris is the longest at a single major by any woman in the Open era.
"There is no expiration date for ambition and for dreams," Cirstea said. "And I have so much passion for this sport. I absolutely love tennis and to be able to still play at this level, have my family, my team, the closest people watching me, it's an absolute joy.
"Sometimes society puts us in certain groups because of the age, but I think in life you are free to do whatever you want and I want to play. And here I am."
Cirstea will next face No. 8 Mirra Andreeva, who defeated Jil Teichmann 6-3, 6-2.
Following a first week marked by a suffocating heatwave, relief finally arrived in Paris on Sunday, with temperatures dropping to 70 degrees around midday.
The Associated Press and PA contributed to this report.