Ronan O’Gara rescued a miraculous win from the jaws of defeat as his injury-time drop goal floored Northampton at Thomond Park.
Trailing 21-20, Munster went back and forth through a mammoth 41 phases as they tried to get the tournament's record points scorer into drop-goal range.
Saints kept their discipline and defended manfully but O'Gara showed his mettle with a superb long-range strike that cruelly denied the visitors a famous Heineken Cup victory on Limerick soil.
It was an incredible finish to an absorbing battle between these two former European champions, with two tries inside the opening nine minutes lighting the touch paper.
Munster were first to strike, hooker Damien Varley piling over on the end of a third-minute lineout maul.
Ryan Lamb missed his first penalty attempt from far out, but Saints were back on terms when Chris Ashton finished off a sparkling move from the back three.
Two penalties from Lamb nudged Northampton into a 13-7 lead, a deserved one given that the visitors looked a little quicker in thought and endeavour.
But a fine score from Doug Howlett in first-half injury-time shot Munster ahead at the break, and O'Gara kept his side on course.
But Northampton dug into their reserves of energy and began to force the issue around the hour mark, with former Munster centre James Downey grabbing an unconverted try.
That was the lead score until Saints hearts were broken by O'Gara's magical match-winning kick.
An early steal from Niall Ronan and some terrific hounding from Heineken Cup debutant Peter O'Mahony set up a five-metre lineout for the men in red.
Varley's throw was taken in by Donnacha Ryan and a thunderous maul saw Munster steamroll their way over the line. O'Gara's conversion made it a seven-pointer.
Northampton regrouped well however and Lamb was only just short from a monster penalty effort from the left.
But then Munster kicked possession away and Saints needed no second invitation.
Recent signing Vasily Artemyev offloaded brilliantly out of a tackle near halfway and Ashton unleashed Ben Foden down the left wing. The hosts were caught for numbers and Foden drew in the covering Howlett, allowing Ashton to finish with aplomb in the corner.
Lamb, who had to be treated for a facial wound, added the extras and fired over a well-struck penalty to put Saints ahead for the first time.
Munster raised the tempo with another forceful lineout drive but Ronan blundered when peeling away and throwing a forward pass to Conor Murray.
The already red-hot atmosphere was cranked up by a couple of skirmishes between the forwards, but Lamb steadied Saints with another sure-footed penalty goal.
Jim Mallinder's men tried to exert pressure in the scrum where Soane Tonga'uiha faced off against BJ Botha, however as the half came to a close the set-piece decisions were going Munster's way.
Murray profited from some quick clearing out, sniping through and linking with Danny Barnes who took play into the visitors' 22. Howlett then prized open a midfield gap and danced past a flatfooted Foden to score by the posts.
O'Gara converted and swapped penalties with Lamb early in the second half, with both sides enjoying spells of supremacy.
Foden was in the wars after shipping a hard hit from Howlett and putting his body on the line to bring down Denis Hurley.
His efforts summed up the determination of a Northampton side still sore from their final defeat to Leinster last May. Lee Dickson and Lamb controlled possession behind an increasingly influential pack.
They made the most of a breaking ball to put the strong-running Downey over on the left for their second try of the night. It was a deserved try given the previous phases and Lamb's missed conversion was to prove important in the end.
Munster threw the kitchen sink at Northampton in a high-energy finish, without truly making an incision. Indeed, Saints went closest to touching down again when Artemyev knocked on with the line in his sight.
Will Chambers was a lively runner for the home side and John Hayes, becoming the first player to make 100 Heineken Cup appearances, was introduced up front.
O'Gara missed a long-range penalty from the left and Northampton's defence seemed capable of riding out the result until the Corkman added another improbable plotline to the province's Heineken Cup story.