Gold medal favourite Iga Swiatek began her Olympic bid with a testing victory over Irina-Camelia Begu in Paris.
Polish world number one Swiatek has won the past three French Open titles at Roland Garros and is almost untouchable on clay.
But she had to fight hard in a tight second set to see off the Romanian 6-2 7-5.
Swiatek, who has won 22 matches in a row at Roland Garros, will face either Nadia Podoroska or Diane Parry in the second round.
Italy's Jasmine Paolini, runner-up to Swiatek in the French Open showpiece in June, also advanced with a 7-5 6-3 win over Ana Bogdan of Romania.