Tries from wingers Doug Howlett and Keith Earls, allied to a late penalty try, helped Tony McGahan's men bring the European Cup winners back down to earth.
McGahan called for attitude and intensity from Munster and he got it in spades as the province lifted the league title for the second time in three seasons at Thomond Park.
Table toppers since round 2 of the competition, Paul O'Connell and his team-mates outfought a tired-looking Leinster side who could only muster three penalties from Jonathan Sexton.
Fresh from a weekend off, Munster fielded an unchanged starting line-up from their 18-11 semi-final defeat of the Ospreys.
Gordon D'Arcy's ankle injury saw Fergus McFadden join Brian O'Driscoll in the centre for Leinster, who reintroduced Heinke van der Merwe and Shane Jennings in the pack.
It was a win apiece earlier in the campaign - Leinster were 13-9 winners at the Aviva Stadium and a Ronan O'Gara-inspired Munster claimed a 24-23 triumph in Limerick last month - and there was a typically bruising opening to the grand final.
Sexton miscued a long range penalty with the wind behind him, six minutes in, and although Leinster won a series of early turnovers, Munster were showing much more in attack.
Twice Howlett was put into space on the right and on the third occasion, the excellent Lifeimi Mafi danced away from Eoin Reddan to send the former All Black over in the corner for the opening try.
O'Gara read the wind superbly to stab the conversion over, rewarding his forwards for an energetic start. The tireless O'Connell and man-of-the-match David Wallace were both to the fore, the latter keen to impress in his 200th outing for Munster.
The turnover rate was high as the sides scrapped for every ball. Munster exerted more control through O'Gara and Conor Murray, with Leinster having to attack from deep.
One such counter led to a cynical shoulder charge by Marcus Horan on O'Driscoll which was missed by the match officials. A subsequent scrum infringement saw Sexton split the posts from a central position.
Closing in on half-time, Murray sparked a break that might have led to a try and O'Gara's hurried drop goal attempt lacked conviction.
A sparkling run and pass from O'Driscoll got Leinster immediately into scoring range after the break. The visitors' forwards battered away at Munster's defensive line until Donncha O'Callaghan was sin-binned for not rolling away in front of his posts.
Sexton took the three points on offer and Munster staved off Leinster's next assault on their line - Richardt Strauss and McFadden, tackled brilliantly by Wallace and James Coughlan, were both thwarted.
A looping pass from Sexton was mishandled by McFadden as Munster were caught for numbers out wide, but the Leinster out-half was successful with a right-sided penalty soon after for a 9-7 lead.
With just 20 minutes remaining and tension all round, it was anybody's game. Munster then barged back to within metres of the Leinster line, a thunderous tackle from Luke Fitzgerald knocking Howlett to the ground just when a try looked on.
But Munster turned the screw when O'Gara lofted a cross-field kick over to Earls who avoided Isa Nacewa's initial challenge and dotted down despite a despairing tackle from Shane Horgan.
O'Gara was narrowly wide with the left-sided conversion and watched his 48-metre penalty miss the target, with nine minutes remaining.
However, Leinster's hopes were extinguished by the concession of a third try. One of their strengths all season, the scrum, let them down as Munster drove them back at an alarming rate on two occasions and referee Nigel Owens signalled for a penalty try.
O'Gara's conversion took the lead to 10 points and Leinster were even denied a meaningless late try as both Kevin McLaughlin and Nathan Hines were stopped by Munster's red wall of defenders.
The victory was Munster's 21st in 24 Magners League matches this season and saw them complete an unbeaten 13-match run at home over the campaign.
The province's third league title - they were also winners in 2003 and 2009 - also draws them level with the Ospreys on the roll of honour.
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