Their opponents in the mouth watering all-Ireland tie, Leinster, have made it to this stage for the fourth time, although they have never lifted the trophy.
Cardiff Blues, who next week face Gloucester in the EDF Energy Cup final at Twickenham, have reached the European semi-finals for the first time since the region was formed.
The Blues did so with a 9-6 victory over French aces Touluse, however their forerunners, Cardiff RFC, played in the very first Heineken Cup final at the Arms Park.
Director of Celtic Rugby David Jordan said: "Congratulations must go to all the teams for their performances over the weekend.
"It is a clear reflection of the success that Magners League teams and their players now enjoy when they transcend into other tournaments.
"With the RBS Six Nations trophy once more safely secured in Celtic hands, there is now all to play for to ensure that the Heineken and EDF Energy Cups will both be retained by Magners League teams. Good luck to all those taking part."
The Magners League resumes this coming weekend with all four Irish provinces in action.
Ulster and Leinster are both away to Scottish sides on Friday - Glasgow Warriors and Edinburgh respectively - while Munster and Connacht will face off in a top-versus-bottom provincial derby at Thomond Park on Saturday.
