Ronaldo opened the scoring early on before Galatasaray mounted a sensational rally with goals from Emmanuel Eboue, Wesley Sneijder and Didier Drogba.
However, Ronaldo sealed the deal in injury time to give the Spaniards a 5-3 aggregate win despite the 3-2 setback on the evening.
Madrid now advances to the last four of Europe’s most prestigious club competition for the third consecutive year under Jose Mourinho.
The Spanish Liga champions sprinted out of the starting blocks and almost stunned the Turk Telekom Arena faithful when Gonzalo Higuain found some space and unleashed a shot that Gala keeper Fernando Muslera did well to block.
However, Muslera did not stand a chance in the eighth minute when Ronaldo’s side-footed effort eluded him and found the back of the net.
It was 1-0 for Real Madrid on the evening and 4-0 on aggregate and the tie seemed all but over and the visitors took their foot off the gas pedal accordingly.
Mourinho’s men were content with their 1-0 advantage heading into the interval but little did they know all hell was about to break loose.
Eboue gave the hosts a glimmer of hope with an absolute rocket that found the top corner before Wesley Sneijder made things very interesting with a low shot that beat Diego Lopez.
Suddenly it was 2-1 for Gala on the night and Drogba then sent the home supporters into raptures when he expertly flicked the ball past Lopez.
The Turkish side was up 3-1 but still down 4-3 on aggregate and had Real Madrid on the ropes. However, the visitors regained their composure and took the sting out of the match much to the chagrin of Gala’s fervent supporters.
Cristiano Ronaldo then scored his second goal of the game deep in injury time to punch Real Madrid’s ticket to the last four.