What is it?
A Wimbledon semi-final between two of the greatest players ever, on Centre Court. This match will be straight after the first semi-final between Novak Djokovic and Roberto Bautista Agut.
Federer and Nadal - with 38 grand slams between them - will surely illuminate what has been an underwhelming men's tournament so far at Wimbledon.
Although they recently met at the same stage of the French Open last month, the 40th instalment of a thrilling match-up is the first at SW19 since the epic 2008 final - widely considered to be one of the best matches ever.
When is it?
Today! Friday, July 12.
What time does it start?
Nadal-Federer will follow the first semi-final between Djokovic and Bautista Agut, which starts at 1pm. We can only guess how long that game will last so best advice is to watch them both and not miss a thing.
What TV channel is it on?
The BBC's Wimbledon coverage starts today on BBC 2 at 12.30pm until 8pm. It will also be on BBC 1 from 1.45pm until 6pm. The Today at Wimbledon highlights show starts at 8pm on BBC 2.
What will the weather be like?
Very nice. Sunny intervals and a moderate breeze with a high of 24 degrees at 3pm, which should be just about when Federer and Nadal take to the court.
Federer and Nadal's rivalry in numbers
40 - This will be the 40th meeting of the two greats. Nadal holds the upper hand with 24 wins to Federer's 15.
70 - Their combined age. Federer turns 38 in August, Nadal is 33.
38 - Grand slam titles between them. Federer has won 20, Nadal is looking for his 19th.
100 - Matches won by Federer at Wimbledon, the first man to reach a century at a single grand slam event.
11 - Consecutive grand slam wins between them, from the 2005 French Open to the US Open in 2007.
9 - Number of games won by Nadal in the deciding set of the 2008 final, the last time they met at Wimbledon.
211 - Consecutive weeks sharing the top two spots in the world rankings, from July 2005 to August 2009.
17 - Nadal's age when they first played each other. The Spaniard beat the then world number one in straight sets, in Miami.
65 - Consecutive grass court victories for Federer, a record run ended by Nadal in the 2008 Wimbledon final.
234,308,576 - Combined career prize money (US dollars).
What are they saying?
Nadal is excited for the next chapter of his enduring rivalry with Federer:
"I am excited about this match, excited about this opportunity to be again in that round against him.
"The opportunities to play against each other every time are less, but we are still here.
"I just expect to play against probably the best player of the history in this surface and know that I have to play my best if I want to have chances to try to be in that final. That's all.
"I know he's playing well. He feels comfortable here. And me, too. I'm playing well."
Federer got the better of Nadal in the final of the Australian Open in 2017 and he believes that might have more significance than the recent loss at the French Open:
"Maybe the Australian Open final. Obviously, best-of-five set match, five sets.
"Then again I don't know. It doesn't matter anyway. Who cares? It's about how has he played so far, how have I played so far. I hope it goes my way.
"It's going to be tough, you know. Rafa really can hurt anybody on any surface. I mean, he's that good. He's not just a clay court specialist, we know."
What are the odds?
Federer to win 6/5
Nadal to win 4/6
What's our prediction?
Nadal has won 24 of their previous meetings, Federer 15, but Centre Court is very much the Swiss' territory and the 37 year-old is looking as dangerous as ever. Rafa has improved considerably on grass in recent years, but knows he is coming up against the greatest on this surface. Prediction: Federer wins in four sets.