The 6-4, 7-6 victory put the 28-year-old former world number three into her first Grand Slam quarter-final since her return to the sport.

She had been away from the tour on maternity leave after giving birth to her daughter last October.

In what was the pair's second meeting on clay, Svitolina raced to a 4-1 lead in the first set but let her opponent creep back into it before regaining composure to take the advantage.

She was then forced to a tiebreak in the second but prevailed by seven points to five thanks to Kasatkina's 45^th unforced error of the match.

"I don't have that pressure that I used to have before," Svitolina said.

"Of course, me personally, I put pressure for myself because I want to win a Slam.

"This is the ultimate goal for me."

She is due to face second seed Aryna Sabalenka of Belarus, who is also competing as a neutral, in the quarter-finals.

Sabalenka battled her way to a 7-6, 6-4 win over 2018 finalist Sloane Stephens of the United States, in the night session match at Roland Garros - the first time in this year's tournament that a women's singles match has been chosen for the slot. 

The women's singles also saw unseeded neutral athlete Anastasia Pavlyuchenkova pull off a 3-6, 7-6, 6-3 upset against Belgian Elise Mertens.

Czech Republic's Karolína Muchová also sealed her place in the next round after cruising past neutral Elina Avanesyan 6-4, 6-3.

In the men's singles, Novak Djokovic dominated Peruvian Juan Pablo Varillas 6-3, 6-2, 6-2 to reach a record 17^th Roland Garros quarter-final.

The Serbian dominated his number 94-ranked opponent in one hour and 57 minutes to book a meeting with neutral Karen Khachanov.

The 11^th seed overcame an early shock from Italy's Lorenzo Sonego to prevail 1-6, 6-4, 7-6, 6-1.

Top seed Carlos Alcaraz of Spain blitzed Sonego's compatriot Lorenzo Musetti 6-3, 6-2, 6-2 prior to Greece's Stefanos Tsitsipas' 7-5, 6-4, 6-0 defeat of Austrian Sebastian Ofner in the day's other singles matches.

Early on in the day, there was controversy in a women's doubles match involving Japan's Miyu Kato and Indonesia's Aldila Sutjiadi.

Kato tried to send a ball back to the service end but accidentally hit a ball girl on the shoulder which initially landed her a warning from the umpire.

However, following protests by opponents Marie Bouzkova of Czech Republic and Spain's Sara Sorribes Tormo, who had won the first set 7-6, but were 3-1 behind in the second set when the incident happened, Kato and Sutjiadi were disqualified.

Competition is set to continue tomorrow with the remainder of the singles round-of-16 fixtures.