With a 1-1 home draw to overcome from the first leg, Jose Mourinho looked on in jubilation as his team executed their gameplan to perfection, frustrating the Catalans at the back, and through an inspirational Cristiano Ronaldo, giving a counter-attacking clinic up front.
The Portuguese opened the scoring from the penalty spot 12 minutes in, becoming the first player to score in six successive Clasicos away from home, and finished off a surging break shortly before the hour mark to put Madrid in the driving seat.
Raphael Varane put the finishing touches on an unbelievable night for the visitors when he headed home a corner, with Jordi Alba's late goal coming as little consolation for the hosts.
Los Blancos now await either Sevilla or Atletico Madrid in the showpiece event on May 18.
Sergio Busquets, Cesc Fabregas and Xavi returned to start in midfield for the hosts, with Carles Puyol partnering Gerard Pique in defence. For Madrid, Varane, the standout performer from the first leg, started alongside Sergio Ramos at centre-back.
Barca started positively, and with only two minutes on the clock, were nearly ahead. Pedro did brilliantly to turn Fabio Coentrao inside out and square for Lionel Messi, who narrowly missed the target from a tight angle.
But instead, it would be Madrid who would take the lead. Ronaldo was simply too quick for Pique, and was tripped up inside the area, leaving the referee with no choice but to award a penalty, from which the Portuguese forward slotted coolly into the bottom corner.
The Catalans exhibited their customary dominance of the ball, but Mourinho’s men were ready with discipline and numbers at the back, and a pacey threat on the counter whenever they won possession.
Referee Alberto Undiano Mallenco, already the villain of the piece in the eyes of the Camp Nou faithful for the decision against Pique, was showered with further vitriol from the stands after correctly denying penalty appeals for Fabregas and Pedro.
And the home fans were left frustrated again moments before half-time, when Messi drilled a free kick agonisingly into the side netting, with half of the stadium already celebrating a goal.
The Blaugrana went close again minutes after the restart when Diego Lopez parried an effort by Busquets, with Alvaro Arbeloa taking the rebound off the toes of Fabregas from point blank range.
But much like the start of the first half, the chance was spurned, and again, Madrid would punish their profligacy on the counter-attack, this time putting the tie virtually out of reach.
Sami Khedira’s sublime first-time pass after winning the ball released Angel Di Maria against Puyol. The Barca captain was left on his backside by the skill of the winger, whose initial shot was parried by Jose Pinto, only for Ronaldo to bury the rebound.
And with 22 minutes left, Madrid were in dreamland again, when Varane rose highest to head home Mesut Ozil’s corner in almost identical fashion to his goal in the first leg.
Flares were set off in the stands as a few home fans lost patience with events on the pitch, but their mood improved ever so slightly just before injury time when Alba ghosted in behind the full-back to slot Andres Iniesta's clipped pass beyond Lopez.
But the damage was long done by the irrepressible visitors, who will now contest the final in three months. The Clasico drama is not quite done, however, as both sides will lock horns at Santiago Bernabeu in la Liga on Saturday.