Paul-Henri Mathieu won an epic match against John Isner that went to the 34th game of the fifth set.
The French wildcard eventually overcame the American 6-7 (2-7) 6-4 6-4 3-6 18-16 in five hours 41 minutes.
Isner played the longest match in Grand Slam history, beating Nicolas Mahut 70-68 in the deciding set at Wimbledon in 2010 after 11 hours and five minutes.
Mathieu's win was the second longest match in French Open history and the fourth longest in Grand Slam history.
The Frenchman, 30, took his seventh match point to progress to the third round.
The duo's 76-game contest set a French Open record for most games played, surpassing the mark shared by four matches, since tie-breaks were introduced in 1973.
Isner hit 41 aces but had 98 unforced errors on the way to defeat by Mathieu, ranked 261 in the world, who returned from a 15-month lay-off with a knee injury in January.
Mathieu said: "I find it hard to realise that I won that match.
"I play tennis to live moments like these. If I worked so hard to come back, it was to experience moments like this."
Isner said: "I just didn't get it done. I felt like I got caught in patterns that weren't ideal for me.
"I wasn't going for my shots at certain points in the match, and that comes from a little bit of a lack of confidence."
He added: "It stinks that I lost. I am just going to go home, I don't want to think about tennis right now."