Elena Baltacha overcame American Sloane Stephens to ensure two British women will contest the French Open second round for the first time since 1992.
The 27-year-old Scot won 7-5 6-2 in 83 minutes to join Heather Watson in advancing past the first hurdle.
Britain has not had two female players achieve that feat since Jo Durie and Sara Gomer did so 19 years ago.
Baltacha, who has never passed the third round of a Grand Slam, will next play another US player, Vania King.
The world number 115 upset 22nd seed Dominika Cibulkova with a 6-7 (10-12) 6-3 6-2 triumph on Court Three.
But 83rd-ranked Baltacha goes into their meeting as the favourite and she will be full of confidence following her win over Stephens.
"I've got to say that was the most satisfying win I think of my whole career," said Baltacha.
"Last year I was in the main draw, but the nine years before that I've been turning up here to Paris and been going home the same night because I had been losing first-round qualifiers every year."
"This year I'm so happy I listened to my coach Nino Severino, because he was trying to persuade me to have a proper clay season for the last couple of years."
There was little to choose between Baltacha and Stephens in the early stages of their match on a sparsely-populated Court Six, the scene of against Stephanie Foretz Gacon 24 hours earlier.
Serve dominated and neither player faced a break point until game six, when Stephens cranked up the pressure and managed to strike as Baltacha went long with a backhand.
The British number one hit back immediately but was then broken again at 3-4 to leave her 18-year-old opponent serving for the set.
However, the Stephens delivery faltered once more and Baltacha converted the first of two break-back points before holding firm for 5-5.
Sensing her chance to pounce, the Ipswich-based right-hander snapped up a third consecutive break in game 11 and then sealed the set when Stephens mishit a return.
Both women made a positive start to the second set but this time it was Baltacha who made the first move to break for a 2-1 lead and then hold to love for 3-1.
With Stephens' unforced-error count on the rise and her serve malfunctioning, Baltacha pressed ahead and secured the double-break in game seven.
She served out for the win on her second match as Stephens flashed a forehand into the tramlines.