Real are still without first-choice midfield duo Casemiro and Toni Kroos and centre back Pepe, but coach Zinedine Zidane said the team would be lifted by the return of Ramos.
"He's our captain and we're so happy that he is back with us," Zidane told a news conference on Friday.
"He's vital for the group on and off the pitch. He's a great player and a great person."
The return of Benzema is timely for Real, who lost fellow centre forward Alvaro Morata for up to a month to a hamstring injury sustained during Spain's 2-2 draw with England on Tuesday.
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Real top the standings on 27 points, two ahead of second placed Barcelona and six clear of Atletico in fourth.
Real have not beaten Diego Simeone's side in the league since 2013 and can expect an even more hostile atmosphere than usual in the final derby at the Vicente Calderon stadium before it is demolished.
"The Calderon is a spectacular stadium filled with great supporters but Real Madrid know it well and we're used to it," Zidane said.
"The derby is not an exam for me, it's just another league game but it'll be very tight. We'll have to give our all in every aspect of the game. It'll be a very difficult game but we're used to difficult games.
"It's not just a special game for me, but for all Real Madrid fans. People talk a lot about the hate in these games but for me it's magnificent to be a part of these games. It could be my last game at the Calderon, so I want to enjoy it."
(Reporting by Richard Martin,editing by Neil Robinson)
