Similar to what happened to Barcelona on Tuesday night, Madrid almost got eliminated from the tournament after conceding three goals at the Santiago Bernabeu but for the timely intervention of Portuguese forward who scored a penalty to push the team through.
Gianluigi Buffon was infuriated by referee Michael Oliver's decision to award Madrid a penalty in the 93rd minute and was sent off for his aggressive reaction but Marcelo insisted there was no doubt over the spot-kick.
Elsewhere, it was a more routine affair with Bayern Munich holding Spanish side Sevilla to a goalless draw in the Bavarian city, to advance with a 2-1 aggregate score over the two legs.
Cape Town - Cristiano Ronaldo showed an fantastic ability to handle the biggest of occasions when he stepped up to coolly score a stoppage-time penalty for Real Madrid against Juventus. Substitutes: Lucas Vasquez (for Casemiro, 45) 6, Marco Asensio (for Bale, 45) 6, Mateo Kovacic (for Modric, 75) 6.
Mario Mandzukic scored as early as 90 seconds to set the ball rolling for the Old lady and added another header in the 37th minute.
The Welsh forward didn't start last season's Champions League final victory over Juventus in Cardiff, and he hasn't been a regular even when fit this season.
Real Madrid will be the semi-finals for the eighth successive time.
Bruña initially wrote: "A penalty was what it was, as Benatia mowed down Lucas Vázquez in the last play of the game".
Marcelo insisted Real Madrid were never going to capitulate like fierce rivals Barcelona after the Champions League titleholders dramatically survived against Juventus.
The match looked destined for extra time until the referee's penalty decision.
"I'm disappointed that they say we're through because of the referee".
He said: "I knew we would be up against it, but I didn't expect what happened in the first minute".
"We could've scored five or six goals tonight, so we ought to be proud".
The twelve (12) times champions of the competition went to the Juventus Arena when the two sides met in the first leg of the tie and won by three goals to nothing.