That is according to Rod Laver, who many people around the world think that title currently belongs to.
Laver won 11 Grand Slams between 1960 and 1969, but he believes Federer has now taken that acclaim after he won his 20th Major at the Australian Open.
The Swiss star showed supreme resilience to edge Maric Cilic in a five set thriller on Sunday morning.
Federer, 36, seems to get better with age and Laver thinks he has now earned the right to be called the best player to ever play tennis – even more so than current world No1 Rafael Nadal.
“For me, I think Roger Federer is certainly the greatest player that has come along,” Laver said.
“Yes, we’ve got lots of great players — look at (Rafael) Nadal with a record that says ‘I’ve just won 10 French Opens’, and you can’t sort of push that under the mat.
“But I think Roger plays is greatest tennis on the big occasions, on any surface.
“He’s stood the test of time — that’s probably the one thing that puts you in that category of the best ever.
“That’s one of the things that he has done. He loves the game, and everything he does around his life is somewhere related to all the great (things he has done).
“It’s just unusual to see a wonderful champion like that be able to win at age 36 after seven tough matches.
“You just marvel at his tenacity and his floating ability on the court.
“He just seems like he’s floating all around the court — he’s not running. That’s something else.”