Winger Simon Zebo scored a second-half hat-trick as Munster ended Northampton's European dreams with a dazzling Heineken Cup Pool One win.
They were level at 19-19 at half-time, with Saints scoring a penalty try and BJ Botha crossing for Munster.
A rapid double from Johne Murphy and Zebo saw Munster take control.
The hosts scored a second penalty try but Zebo went over twice more and Scott Armstrong's late score was little consolation for shellshocked Saints.
The hosts went into the game knowing they had to win with a bonus point, and hope other results went their way, to stand any chance of reaching the Heineken Cup last eight as one of the two best runners-up in the six pools, although a more realistic ambition was to claim a Challenge Cup place as one of the third to fifth-best placed runners-up.
With their mighty scrum on top from the opening exchanges it looked as though it might lay the platform for last season's beaten Heineken Cup finalists to avenge their narrow defeat in Munster in the first match of this year's competition.
However, Munster were superior in every other department and when they cut loose in the second half Saints had no answer.
Two penalties from Northampton fly-half Ryan Lamb to one from Munster counterpart Ronan O'Gara - who kicked 24 points - made it 6-3.
The massive power of the Northampton eight then earned the first of their penalty tries at a scrum but they could not shake Munster off and the visitors hit back through a converted BJ Botha score.
A flurry of successful kicks from the two fly-halves made it 19-19 at half-time and Munster then ran riot.
Murphy stepped inside the cover to finish off a sweeping move and some excellent passing from the backline sent the flying Zebo clear down a narrow channel on the outside to secure a spectacular score.
O'Gara converted both but Northampton gave their vocal fans belief they could fight back as they once again butchered Munster at a scrum to earn a second penalty try.
That made it 31-26 but Munster were now playing with total confidence and Zebo picked off an interception try and then scissored sweetly to complete his hat-trick.
O'Gara's boot kept the scoreboard ticking over and although Armstrong crossed late on for Northampton, they had been well beaten in an absolute belter of a contest in front of over 22,000 at Stadium mk, Northampton's second home.
Northampton coach Jim Mallinder: "They raised their game from their previous five in the Heineken Cup. They looked after the ball and we gave it away.
"You talk about getting your set-piece right but, while our scrum was good, our re-starts meant we couldn't get out of our own half.
"You can't just have dominance in the scrum and expect to win the game. Munster dominated every other area and came out on top.
"We were competing against one of Europe's best sides and, while we did well in Munster and could easily have won, today we came second best.
"What they did very well was slow us down in the contact area. We couldn't get on the front foot and get the ball wide.
"They have a good chance now. They raised their game and I thought they were very good."
Munster captain Paul O'Connell: "That has been coming for a while. We've been close and it was satisfying to see the back line finishing off a few moves. It's right up there because it came against a good side away from home at the business end of the Heineken Cup.
"That 10-minute period just after half-time gave us a real lift. To be under such pressure in the scrum and still come out on top is testament to the strength and heart of the team.
"Last year didn't go our way, but we've had a bit of luck this season and worked very hard to go six from six. We've still got a bit of a way to go to get up to the standard of Toulouse and Leinster.
"We've proved nothing yet - we've just come out of our pool and won nothing. We've got a long way to go to emulate the teams of 2006 and 2008 who won the tournament."
Northampton: Foden; Elliott, Pisi, Downey, Artemyev; Lamb, Dickson; Tonga'uiha, Hartley, Mujati, Manoa, Sorenson, Clark, Dowson, Wilson.
Replacements: Armstrong for Elliott (68), Myler for Lamb (72), Roberts for Dickson (72), A. Waller for Tonga'uiha (66), Doran-Jones for Mujati (64), Day for Sorenson (62), Nutley for Clark (62).
Not Used: Sharman.
Sin Bin: Dickson (56).
Munster: D Hurley; Murphy, Earls, Mafi, Zebo; O'Gara, Murray; du Preez, Varley, Botha, D. O'Callaghan, O'Connell, D. Ryan, O'Mahony, Coughlan.
Replacements: Keatley for O'Gara (74), O'Leary for Murray (67), Fogarty for Varley (74), Archer for Botha (72), O'Driscoll for D. O'Callaghan (72), D. O'Callaghan for O'Mahony (72).
Not Used: Horan, Barnes.
Sin Bin: Murray (56).
Ref: Romain Poite (France).