Two-time major champion Rybakina made a bright start on Court Suzanne Lenglen, racing to a 5-1 lead before her game started to unravel.

Rybakina was able to see out the opener but Starodubtseva won nine of the next 10 games to level the match and go 3-0 up in the decider.

Rybakina never looked convincing despite clawing her way back from a double break down to force a tie-break, and a double fault on the opening point was a sign of things to come.

Starodubtseva continued to play aggressively to storm ahead and wrap up the biggest victory of her career.

It is a second French Open upset in as many years for Ukraine's Starodubtseva, having beaten 2024 runner-up and fourth seed Jasmine Paolini in the second round last year.

"I'm super happy. Elena is one of the top players, she's had an incredible year and I'm super proud of myself that I was able to do this today," Starodubtseva said.

She will face American 26th seed Hailey Baptiste or China's Wang Xiyu next.