“I have always had the utmost respect for my friend Rafa as a person and as a champion,” Federer, who already owned four Grand Slam titles when Nadal won his maiden French Open title in 2005, said on Twitter.
Roger Federer saw his men's record haul of 20 Grand Slam singles titles matched by Rafa Nadal on Sunday and the Swiss great was quick to offer his congratulations to the Spaniard.
Nadal crushed Serbia's world number one Novak Djokovic 6-0 6-2 7-5 to claim a 13th French Open title and move level with Federer for the first time in his career.
"I have always had the utmost respect for my friend Rafa as a person and as a champion," Federer, who already owned four Grand Slam titles when Nadal won his maiden French Open title in 2005, said on Twitter.
"As my greatest rival over many years, I believe we have pushed each other to become better players.
"Therefore it is a true honour for me to congratulate him on his 20th Grand Slam victory."
Nadal, 34, has lost only two matches at the French Open, racking up his 100th win on Sunday.
"It is especially amazing that he has won Roland Garros an incredible 13 times, which is one of the greatest achievements in sport. "I also congratulate his team because nobody can do this alone."
Federer turned 39 in August and missed the U.S. and French Opens while recovering from an injury, but he has vowed to be back at the Australian Open next year.
"I hope 20 is just another step on the continuing journey for both of us," the Swiss said.
"Well done Rafa, you deserve it."
Djokovic is third on the list with 17 Grand Slam titles.