Two yellow cards cost the French side as they conceded 28 points when down to 14 men, unable to cope with the canny flair and forward power of a Leinster side that had a man advantage for 20 minutes and a roaring crowd behind them.
Number eight Jack Conan bagged two tries to go with scores from hooker Dan Sheehan, flanker Josh van der Flier and replacement loose-forward Jason Jenkins, with four of those tries coming when Toulouse were a man down.
Centre Pita Ahki, lock Emmanuel Meafou and flanker Jack Willis crossed for the record five-time champion visitors, who lost 40-17 to Leinster at the same venue in last season’s semis and were hit by a bout of deja vu much of their own making.
Leinster, made up almost entirely of players who helped Ireland to the Six Nations title this year, now await the winner of Sunday’s second semi-final in France between La Rochelle and Exeter Chiefs.
Leinster, who have four Champions Cup titles, were beaten 24-21 by La Rochelle in last season’s final. This time it will be hosted at their Aviva Stadium home on May 20, giving them an enormous advantage.
"We are absolutely delighted. It was the toughest game we have played all season," Leinster captain James Ryan told BT Sport. "Just defensively it is such a challenge playing Toulouse as they are probably the best-attacking side in Europe.
"I thought we managed the game well and during those periods when they got those yellow cards. We are happy enough but the job is far from done yet. There is plenty we can get better at. We are going to have to get better for the final again."
Toulouse started on the front foot and scored the opening try through Ahki, but once full-back Thomas Ramos was sent to the sin-bin for a deliberate knock-on the game swung in Leinster’s favour.
Conan scored two quick tries as the hosts moved into a 20-7 lead and, soon after Ramos’ return, they added a third as a knock-on near their 22 from the visitors allowed Sheehan to coast in for the score.
The first quarter of the second half was tight before more Toulouse indiscipline cost them the tie.
Prop Rodrigue Neti was sent to the sin-bin for a dangerous tackle on Van der Flier and again Leinster made their advantage count as they scored two more tries while he was off the field.
