Joey Carbery shot down his former side with a 14-point kicking contribution as Munster defeated 14-man Leinster 26-17 in a feisty Guinness PRO14 derby at Thomond Park.
The defending champions' discipline really let them down during a fiery first half, with props Cian Healy and Tadhg Furlong both sin-binned and Kiwi star James Lowe sent off for taking out Andrew Conway in the air.
The unerring Carbery landed two penalties to add to Chris Cloete's 13th-minute maul try, giving Munster a 13-3 half-time lead.
Leinster's maul delivered a 47th-minute try for James Tracy, adding to Jonathan Sexton's earlier penalty and cancelling out Carbery's third penalty success, but the latter nailed a 64th-minute place-kick.
Keith Earls' intercept try had Munster out of reach before replacement Max Deegan's late consolation score.
There was plenty of niggle for referee Frank Murphy to deal with inside the opening quarter, an early scuffle between Fineen Wycherley and Sexton setting the tone. Both fly-halves missed touch with penalties and the visitors had nothing to show for a strong start from their back-line.
The Munster attack clicked superbly in the 12th minute when a clever midfield move off a lineout sent Earls haring over halfway.
Scott Fardy's high tackle on Cloete led to Munster going for the corner and a powerful lineout drive ended with Cloete grounding the ball and Carbery landing the difficult conversion.
Despite Healy seeing yellow for a flailing arm on Conor Murray, a similar infringement by the latter allowed Sexton to open Leinster's account from the tee.
They managed the sin-bin period well, but were down to 14 again after Furlong was binned in the 29th minute for barging into Cloete at a ruck and making no attempt to wrap. The South African had to be carried off on a stretcher.
Barely two minutes later, Lowe's full-tilt challenge for a high ball upended the airborne Conway, who landed on his head.
A TMO review led to referee Murphy brandishing his red card and Carbery closed out the first half with two well-struck penalties, punishing tackle and scrum offences by James Tracy and Michael Bent.
Carbery opened the second half's scoring with a penalty, but pressure from successive lineouts a few metres out saw Leinster hit back with Tracy's maul effort, converted by Sexton.
After Conway went close from a rapid counter-attack, Munster's man of the match Tadhg Beirne duly foiled the Blues' next attempt to build from out of touch.
Leinster, who lie 16 points clear at the top of Conference B, looked to their bench for the final quarter with youngster Ciaran Frawley replacing Sexton.
Carbery's reliable right boot nudged Munster onto 19 points, and just as the visitors threatened in the 71st minute, Frawley's pass was picked off by Earls who raced out of his 22 and all the way to the line with replacement Tyler Bleyendaal converting.
Jack Conan's bulldozing carry led to fellow back rower Deegan touching down past the 80-minute mark, but there was no denying Munster as they overcame their arch rivals for the first time in two years.
Munster: Mike Haley; Andrew Conway, Dan Goggin (Darren Sweetnam 65), Rory Scannell, Keith Earls; Joey Carbery (Tyler Bleyendaal 70), Conor Murray (Alby Mathewson 74); Dave Kilcoyne (Jeremy Loughman 70), Niall Scannell (Kevin O’Byrne 76), John Ryan (Stephen Archer 58); Jean Kleyn (Billy Holland, 65), Tadhg Beirne; Fineen Wycherley, Chris Cloete (Arno Botha 29), CJ Stander (captain).
Leinster: Jordan Larmour; Rory O'Loughlin, Garry Ringrose (Conor O'Brien 68), Noel Reid, James Lowe; Johnny Sexton (captain) (Ciarán Frawley 60), Luke McGrath (Hugh O'Sullivan 74); Cian Healy (Peter Dooley 60), James Tracy (Bryan Byrne 60), Tadhg Furlong (Michael Bent 68); Scott Fardy, James Ryan (Ross Molony 74); Rhys Ruddock (Michael Bent 35-39), (Max Deegan 65) Josh van der Flier, Jack Conan.
Referee: Frank Murphy (Ireland)