World number one Novak Djokovic reached his 16th consecutive Grand Slam quarter-final while seven-time champion Rafael Nadal marked his 27th birthday by also reaching the French Open last eight Monday.
Top seed Djokovic carved out a 4-6, 6-3, 6-4, 6-4 win over 16th seed Philipp Kohlschreiber with the German paying a high price for converting just two of 13 break points.
World number one Djokovic goes on to face German 35-year-old Tommy Haas, who became the third oldest man to reach the last-eight with a comfortable 6-1, 6-1, 6-3 win over volatile Russian Mikhail Youzhny.
Nadal, bidding to become the first man to win the same Grand Slam title eight times, trounced Japanese 13th seed Kei Nishikori 6-4, 6-1, 6-3.
It was third-seeded Nadal's 56th win in 57 career matches at Roland Garros.
The defending champion next faces either French seventh seed Richard Gasquet or Stanislas Wawrinka, the Swiss ninth seed, with a potential semi-final blockbuster with Djokovic just around the corner.
"I needed to earn my victory, and in the end it was good. I'm really glad to get through, because he's a good quality opponent and he's a specialist for this surface," said Djokovic of Kohlschreiber.
On facing 12th-seeded Haas, against whom he has a 4-3 winning record, the Serb said: "I have a lot of respect for Tommy. He is playing well."
Djokovic, the runner-up to Nadal last year, needs a French Open title to complete a career Grand Slam.
The last time he failed to reach the last-eight of a major was in Paris in 2009 when he lost in the fourth round to Monday's opponent.
Nadal arrived in Paris having collected six titles in eight finals since his return from a seven-month injury lay-off.
But he was sluggish in the first week of a cold and damp Paris, losing the opening set of his first two matches.
Since the weather has improved, so has the Spaniard, seeing off Fabio Fognini in straight sets on Saturday and then comfortably defeating Nishikori, the first Japanese man in the fourth round since Fumiteru Nakano in 1938.
"It's a very special moment," said Nadal, as the crowd welcomed him to Court Philippe Chatrier by singing 'Happy Birthday' and repeating it on the match's conclusion.
"Today I think I played my best match of the tournament."
Nadal was presented with a giant birthday cake at the end of the match and he will be looking for more celebrations on Wednesday in the quarter-finals as he holds a 10-0 career lead over Gasquet and 9-0 over Wawrinka.
Haas became the first German in 17 years to reach the quarter-finals and the oldest man to make the last eight at any Grand Slam since Andre Agassi at the 2005 US Open.
Haas, who made history in the third round when he needed a record 13 match points to beat John Isner, eased past Youzhny in just 84 minutes.
"It was a pretty good performance. I was broken in the first game but I got my bearings, got into the groove," said Haas, who is enjoying a renaissance in a career which has been decimated by a series of injuries.
Only Pancho Gonzales, who was over 40 when he made the last eight in 1968, and 39-year-old Istvan Gulyas in 1971, have got this far in the tournament at Haas's age.
Former world number two Haas had lost on clay in straight sets to Youzhny in Rome last month.
But he was never troubled on Monday, winning 10 games in succession after losing the opener.
Such was Youzhny's frustration that he smashed his racquet nine times against his courtside chair, sending splinters spiralling into the air at Court Suzanne Lenglen.
The violence of his outburst made him an instant YouTube hit even as the match was still being played.
"You try and do all you can to help yourself. I tried it this way, but it doesn't help really," said 29-year-old Youzhny.