Four-time champion Iga Swiatek exited the French Open on her 25th birthday after a straight-sets fourth-round loss to the in-form Marta Kostyuk.

The Polish third seed struggled with errors throughout as Ukrainian 15th seed Kostyuk secured a 7-5 6-1 victory on Court Philippe Chatrier.

Swiatek, known as the Queen of Clay after four Roland Garros titles, has not claimed a clay title since her 2024 Paris success.

The six-time Grand Slam winner, set to defend her Wimbledon crown at the end of June, remains without a tournament victory in 2026.

Kostyuk arrived at the French Open unbeaten on clay this year after capturing the Madrid Open title earlier this month and the Rouen Open in April.

"I am still surprised to defeat such an outstanding player who has won here four times," Kostyuk said.

"I feel I have created more room to express myself and test my opponents. I woke up thinking what an incredible day lies ahead and there was nothing else I wanted to do."

Kostyuk will face fellow Ukrainian Elina Svitolina in the quarter-finals following the seventh seed's 4-6 6-4 6-0 victory over Switzerland's Belinda Bencic.

Meanwhile, Romanian 18th seed Sorana Cirstea reached her second French Open quarter-final, 17 years after her initial last-eight appearance at Roland Garros.

The 36-year-old, who intends to retire at the end of the year, defeated Chinese qualifier Wang Xiyu 6-3 7-6 (7-4).

The result extends Cirstea's strong late-career form after her 6-0 6-0 win over Solano Sierra in the third round.

Cirstea described her final season as going better than anticipated yet she has no plans to alter her retirement decision.

"I am taking it week by week and will not change anything or add pressure," Cirstea said. "We will review matters as they develop, but the decision stands for now."

Cirstea defeated world number one Aryna Sabalenka in Rome earlier this month, and her Roland Garros run marks her strongest Grand Slam performance since the 2023 US Open quarter-finals.

She noted greater maturity at 36 compared with her early career and a fresh outlook.

She added: "When I was younger every match felt like life or death. Winning brought huge joy while losing led to days of tears."

"I retain deep passion and joy for the game, yet it is also my profession."

Cirstea will next meet the winner of the match between Russian eighth seed Mirra Andreeva and unseeded Swiss player Jil Teichmann.