Fran Jones stunned a player ranked 152 places above her and fellow Briton Ryan Peniston ended an eight-match losing streak in French Open qualifying.
Jones, 22, knocked out American Coco Vandeweghe 6-3 6-3, while Peniston beat Turkey's Altug Celikbilek 6-4 6-2 to reach the second round in Paris.
They need to come through two more rounds to reach the main draw of the Grand Slam, which starts on Sunday.
Compatriot Sonay Kartal lost her match, despite having led 6-2 5-1.
Having been on the brink of victory, she lost six games in a row to fall 2-6 7-5 6-4 to Viktoria Hruncakova.