Zinedine Zidane's side beat Paris Saint-Germain 2-1 at the Parc des Princes to secure a 5-2 aggregate win and advance to the last eight of the competition they have won in each of the past two seasons.
Los Blancos now focus their attention back on the Primera Division, where they lie in third, 15 points adrift of leaders Barcelona and seven behind second-placed Atletico.
Here, Goal takes a look at everything you need to know ahead of Madrid's trip to the Basque Country on Saturday...
Real Madrid injuries
Marcelo returned from injury in last weekend's win over Getafe and then started in Paris on Tuesday, while Toni Kroos and Luka Modric were on the bench at Parc des Princes and are also available for selection after making a full recovery.
That means Zidane has a full-strength squad at his disposal for the game against Eibar.
Real Madrid suspensions
Real Madrid have no players suspended for the game at Ipurua.
Real Madrid potential starting line-up
Toni Kroos is set to return in midfield for Real Madrid on Saturday, while Luka Modric could also feature in the Liga clash after recovering from injury.
Isco and Gareth Bale, both substitutes against PSG on Tuesday, are set to be included in the starting line-up, with Marco Asensio and Lucas Vazquez likely to be rested.
In central defence, Nacho should come in for Raphael Varane.
Eibar team news
Eibar are enjoying another spectacular season in La Liga and come into this match in eighth place, with 39 points, meaning they are virtually safe from relegation already.
Jose Luis Mendilibar's men lost 2-0 at home to Barcelona recently, but have won seven and drawn three of their 14 games at Ipurua in the Primera Division this term.
Striker Sergi Enrich is sidelined, with midfielders Fabian Orellana and Fran Rico also missing out through injury on Saturday.
TV channel & kick-off time
Eibar versus Real Madrid kicks off at 13:00 local time on Saturday and will be shown live in the United Kingdom (UK) on Sky Sports Football from 11:55 GMT.
In the United States (US), the match is live on beIN Sports and kicks off at 07:00 ET.
Best Opta match facts
Real Madrid have won in each of their three league trips to Eibar, scoring 10 goals in total (3.3 per game on average).
Eibar have failed to beat Real Madrid in their seven La Liga meetings, losing six of those and scoring just two goals.
Real Madrid are unbeaten in the Basque Country since March 2015 (a 1-0 loss against Athletic Club). Since then, they have played in Euskadi on 10 occasions, winning nine.
Cristiano Ronaldo has scored more than 30 goals in each of the last nine campaigns in all competitions. Only Lionel Messi (10) has a longer current run.
The Portuguese player has been directly involved in four goals in his two league visits to Ipurua (three goals and one assist).