The 17th-seeded Monfils had never advanced past the fourth round at a Grand Slam tournament other than the French Open. He reached the semifinals there in 2008.
Gasquet, ranked 38th, upset sixth-seeded Nikolay Davydenko in the second round. The former top-10 player missed more than two months last year after testing positive for cocaine. He successfully appealed, saying the drug inadvertently entered his system when he kissed a woman at a nightclub. This was his first fourth-round match at a Grand Slam since Wimbledon in 2008.
Gasquet had a chance to serve out the third set at 5-3, but Monfils broke back. He ended the match with his 14th ace.