Leinster reached their first ever Heineken Cup final after producing one of the outstanding performances in the competition's history.
Gordon D'Arcy, Luke Fitzgerald and man of the match Brian O'Driscoll scored the tries in front of a record crowd of 82,208 at Croke Park.
But Leinster's victory was founded on a ferocious defensive performance to which Munster - the odds-on favourites, defending European champions and Magners League champions - had no answer.
Leinster, who had lost their last three Heineken Cup semi-finals, will head to Murrayfield on 23 May to face either the Cardiff Blues or Leicester.
Munster were hot favourites but Leinster were fired by thoughts of revenge. They were outplayed by Munster at the same stage of the competition three years ago and collapsed to a 30-6 defeat.
But Leinster have developed a steeliness since 2006. The proved it in a bruising 6-5 quarter-final victory at Harlequins and proved it again today.
Leinster refused to be cowed by the size of the occasion or the quality of the opposition. Munster had scored 15 tries in their previous three European games, today they scored none.
The crackling atmosphere inside Croke Park was paused for a minute's silence in memory of the late Dr Karl Mullen, who captained Ireland to their first Grand Slam in 1948 and led the 1950 Lions in New Zealand and Australia.
Then came a kick-off that had been anticipated the length and breadth of the country. Two of Mullen's successors - 2009 Lions captain Paul O'Connell and Grand Slam skipper O'Driscoll - led Ireland's red and blue tribes into a pulsating battle.
Shane Horgan returned on the wing after Rob Kearney was ruled out with the mumps while veteran Munsterman Peter Stringer started in place of injured scrum-half Tomas O'Leary.
Munster threatened early after O'Driscoll's clearance was blocked and then almost picked their way through after an electric break from Keith Earls, who ran onto Lifiemi Mafi's offload and raced from halfway deep into Leinster territory.
Earls was eventually dragged down five metres out and when Munster transferred quick ball wide to Ian Dowling, Rocky Elsom was lying in wait to nail the winger and Leinster secured the turnover.
Felipe Contepomi, famously ruffled in that 2006 semi-final defeat, had a point to prove. The Argentinian made two powerful early runs and despite a shanked clearance and wayward long-range penalty he nudged Leinster ahead with a cool drop-goal.
O'Gara responded almost immediately with a penalty after Leinster loose-head Cian Healy had been sin-binned for taking out Dowling off the ball.
Leinster were unbowed. Their defensive pressure, epitomised by Elsom, was intense and they were finding holes in the Munster line.
Elsom crashed onto an inside ball and drew a penalty from the stretched defence but Contepomi suffered an apparent knee injury in the same passage of play.
Johnny Sexton came on and slotted the penalty with his first touch to push Leinster ahead.
As Contepomi left so Healy and Shane Jennings, who had been blood-binned after a blow to the head, both returned and Leinster's tails were up.
Nacewa burst onto a delightful inside ball from O'Driscoll and then floated a pass to D'Arcy, who stretched for the line to score after being grounded by Earls' tackle.
It was Leinster's first try in four European outings.
O'Gara landed a penalty to keep Munster in touch at the interval but soon Leinster had their second try.
O'Driscoll was involved twice as Leinster worked the ball to Fitzgerald, who came in off the left wing past Paul Warwick to score. Sexton's conversion made it 18-6.
Munster reacted badly to the pressure. Twice they built prime attacking platforms inside Leinster's 22 and both times failed to chisel any kind of opening.
As Munster smashed their collective heads against the defiant blue defensive wall, flanker Alan Quinlan was caught on camera apparently eye-gouging Leinster's Leo Cullen.
And Leinster then applied the sucker-punch. O'Driscoll popped up to intercept O'Gara's pass for O'Connell and the Ireland captain raced 70 metres to score under the posts.
Croke Park echoed not to the Fields of Athenry - an anthem so familiar now to these grand European occasions - but to the sound of Sweet Molly Malone.