Jupp Heynckes' newly crowned Bundesliga champions produced a magnificent performance laced with power, intensity and quality to give the Catalan superstars a mauling they will surely find impossible to avenge in the Nou Camp next Wednesday.
This was Barca's worst defeat in Europe since they were beaten by the same scoreline by Dynamo Kiev in 1997, and no team has lost the first leg of a European Cup tie by four or more goals and progressed to the next round.
Barca coach Tito Vilanova gambled and lost on a clearly unfit Lionel Messi - but to suggest this was the prime factor behind this crushing loss is to do a grave disservice to Bayern.
Former Barcelona coach Pep Guardiola will replace Heynckes in the summer but this dignified 67-year-old elder statesman may well leave behind the Champions League trophy.
Thomas Mueller gave Bayern an early lead and their superiority was confirmed when Mario Gomez added a second just after half-time.
Barca's loss to Bayern Munich was their worst defeat in Europe since they were beaten 4-0 by Dynamo Kiev in 1997
Former Chelsea winger Arjen Robben tormented a desperately vulnerable Barcelona defence, adding a third before Mueller got his second near the end to surely put this tie out of even Barcelona's reach.
And all this on the day Bayern wielded their power in the transfer market again by announcing a £32m deal for Borussia Dortmund's brilliant 20-year-old Mario Gotze - heady days indeed for the German glamour club once dubbed "FC Hollywood".
In a fevered atmosphere inside a packed and jubilant Allianz Arena, Bayern looked a team intent on erasing the bitter memories of the Champions League final defeat on penalties by Chelsea on their own ground last season.
Messi was declared fit to play and started for Barcelona despite concerns about the hamstring injury he sustained in the previous round against Paris St Germain. He looked a long way from his usual brilliance - but he was not alone as buoyant Bayern took control of proceedings.
On a pitch that showed signs of being heavily watered, Bayern gave Barca a taste of their own medicine with a high-intensity pressing game aided by the confidence of an outstanding season in which the Bundesliga was secured on 6 April, the earliest it has ever been won.
Bayern should have been ahead inside two minutes when Robben, perhaps selfishly, chose to shoot and saw his effort blocked by visiting goalkeeper Victor Valdes with both Gomez and Franck Ribery pleading for the pass in perfect positions.
The opening goal had been coming and it duly arrived after 25 minutes. Dante's header from Robben's cross was off target but the opportunist Muller arrived at the far post to score, despite Valdes making good contact.
Even though the Spanish side were struggling for rhythm, Barcelona's quality meant danger was never far away. And so it proved as it took a crucial touch from Dante to take Dani Alves' delivery away from the lurking Messi.
But Bayern's spirits rose further four minutes after half-time when they added a second. Valdes was uncertain from Robben's corner and, when Mueller headed back, the arch-poacher Gomez turned in as Barcelona appealed in vain for offside.
Bayern's work-rate and power had restricted Barcelona's attack to few dangerous moments, but there was anxiety for the home crowd when Marc Bartra found space eight yards out only to poke his finish straight at home keeper Manuel Neuer.
The German champions were coming at Barcelona in waves and extended their advantage further as the lively Robben worked his way into the area to score from an angle, although there seemed to be a clear case for an infringement as Mueller blocked off Jordi Alba.
Barcelona's agony was not over yet as Mueller applied another of those trademark close-range finishes from David Alaba's cross to give Bayern an advantage of such command it is difficult to see how it can be retrieved.
Full Time   The referee brings the game to a close.
Arjen Robben has a curled shot. Blocked by Marc Bartra. Short corner taken by Bastian Schweinsteiger.
Arjen Robben takes the free kick.
Booking      Andres Iniesta receives a yellow card for unsporting behaviour.
Andres Iniesta concedes a free kick for a foul on Aguinaga Javi Martinez.
Ramos Jordi Alba concedes a free kick for a foul on Arjen Robben. Arjen Robben takes the direct free kick.
Booking      Ramos Jordi Alba receives a caution.
Substitution      (Bayern Munich) makes a substitution, with Xherdan Shaqiri coming on for Franck Ribery.
Direct free kick taken by da Silva Dani Alves.
Booking      Bastian Schweinsteiger is cautioned.
Bastian Schweinsteiger takes the direct free kick. Franck Ribery is caught offside.
Booking      Alexis Sanchez is shown a yellow card for unsporting behaviour.
Free kick awarded for an unfair challenge on Arjen Robben by Alexis Sanchez.
Franck Ribery concedes a free kick for a foul on Lionel Messi. Lionel Messi takes the direct free kick.
Substitution      Rodriguez Pedro leaves the field to be replaced by David Villa.
Substitution      Claudio Pizarro on for Thomas Muller.
David Alaba provided the assist for the goal.
Goal!  - Thomas Muller -    Bay Munich 4 - 0 Barcelona        A goal is scored by Thomas Muller from close in high into the middle of the goal.  Bayern Munich 4-0 Barcelona.
Thomas Muller takes a shot. Save by Victor Valdes. Arjen Robben takes a shot. Gerard Pique gets a block in.
A cross is delivered by Ramos Jordi Alba, Alexis Sanchez gives away a free kick for an unfair challenge on Bonfim Dante. Free kick taken by Manuel Neuer.
Bastian Schweinsteiger concedes a free kick for a foul on Andres Iniesta. The ball is sent over by Hernandez Xavi, Marc Bartra produces a right-footed shot from close in which goes wide of the right-hand upright.
Assist on the goal came from Bastian Schweinsteiger.
Goal!  - Arjen Robben -    Bay Munich 3 - 0 Barcelona        A goal is scored by Arjen Robben from close range to the bottom left corner of the goal. Bayern Munich 3-0 Barcelona.
Rodriguez Pedro produces a cross, save by Manuel Neuer.
Substitution      Luiz Gustavo joins the action as a substitute, replacing Mario Gomez.
Centre by Philip Lahm, Andres Iniesta gets a block in. The ball is sent over by Philip Lahm, blocked by Gerard Pique. Corner taken left-footed by Arjen Robben.
Lionel Messi takes a shot. Bonfim Dante gets a block in. Corner taken by Hernandez Xavi from the right by-line played to the near post, Marc Bartra takes a shot. Save made by Manuel Neuer.
Alexis Sanchez produces a cross.
The ball is swung over by Franck Ribery.
Da Silva Dani Alves crosses the ball, Jerome Boateng makes a clearance.
The ball is delivered by Ramos Jordi Alba, David Alaba manages to make a clearance.
Hernandez Xavi fouled by Bastian Schweinsteiger, the ref awards a free kick. Free kick taken by Hernandez Xavi.
Ramos Jordi Alba produces a cross, Bonfim Dante manages to make a clearance.
Da Silva Dani Alves sends in a cross, Manuel Neuer makes a comfortable save.
Da Silva Dani Alves challenges Thomas Muller unfairly and gives away a free kick. The ball is sent over by Bastian Schweinsteiger, Header from close in by Arjen Robben misses to the right of the goal.
Arjen Robben concedes a free kick for a foul on Alexis Sanchez. Andres Iniesta restarts play with the free kick.
Effort from inside the six-yard box by Franck Ribery goes wide right of the target.
Free kick awarded for a foul by da Silva Dani Alves on Franck Ribery. Franck Ribery restarts play with the free kick.
Arjen Robben challenges Hernandez Xavi unfairly and gives away a free kick. Ramos Jordi Alba restarts play with the free kick.
Effort from the edge of the penalty area by Thomas Muller goes wide of the left-hand post.
Thomas Muller provided the assist for the goal.
Goal!  - Mario Gomez -    Bay Munich 2 - 0 Barcelona        Mario Gomez scores a goal from inside the six-yard box to the bottom left corner of the goal. Bayern Munich 2-0 Barcelona.
Inswinging corner taken by Arjen Robben,
The assistant referee signals for offside against Andres Iniesta.  Direct free kick taken by Manuel Neuer.
Ramos Jordi Alba restarts play with the free kick.
Booking      Aguinaga Javi Martinez is cautioned.
Andres Iniesta fouled by Aguinaga Javi Martinez, the ref awards a free kick.
The match restarts for the second half.
Half Time    The first half comes to an end.
Hernandez Xavi takes the inswinging corner, clearance by Mario Gomez.
Alexis Sanchez gives away a free kick for an unfair challenge on Aguinaga Javi Martinez. Manuel Neuer takes the free kick.
Arjen Robben challenges Ramos Jordi Alba unfairly and gives away a free kick. Andres Iniesta restarts play with the free kick.
Arjen Robben is flagged offside by the assistant referee. Free kick taken by Ramos Jordi Alba.
Free kick taken by Bastian Schweinsteiger.
Booking      Marc Bartra goes into the book for unsporting behaviour.
Foul by Marc Bartra on Thomas Muller, free kick awarded.
Free kick taken by Hernandez Xavi.
Booking      The referee shows Mario Gomez a yellow card for unsporting behaviour.
Mario Gomez challenges Lionel Messi unfairly and gives away a free kick.
Bastian Schweinsteiger takes the outswinging corner, Ramos Jordi Alba manages to make a clearance.
Free kick awarded for a foul by Andres Iniesta on Aguinaga Javi Martinez. Bastian Schweinsteiger takes the free kick.
Arjen Robben gives away a free kick for an unfair challenge on Alexis Sanchez. Ramos Jordi Alba restarts play with the free kick.
Franck Ribery takes the inswinging corner, Bonfim Dante takes a shot. Blocked by Alexis Sanchez. Inswinging corner taken by Arjen Robben.
Inswinging corner taken by Hernandez Xavi from the left by-line played to the near post, clearance made by Jerome Boateng.
A cross is delivered by Rodriguez Pedro, Bonfim Dante makes a clearance.
Unfair challenge on Aguinaga Javi Martinez by Sergio Busquets results in a free kick. Direct free kick taken by Philip Lahm.
Sergio Busquets fouled by Aguinaga Javi Martinez, the ref awards a free kick. Andres Iniesta restarts play with the free kick.
The assist for the goal came from Bonfim Dante.
Goal!  - Thomas Muller -    Bay Munich 1 - 0 Barcelona        Thomas Muller scores a headed goal from close range. Bayern Munich 1-0 Barcelona.
The ball is sent over by Arjen Robben,
Corner taken right-footed by Franck Ribery to the near post, clearance made by Ramos Jordi Alba.
Victor Valdes fouled by Aguinaga Javi Martinez, the ref awards a free kick. Victor Valdes takes the direct free kick.
Arjen Robben takes the inswinging corner, save made by Victor Valdes.
The assistant referee flags for offside against Arjen Robben. Indirect free kick taken by Victor Valdes.
Arjen Robben decides to take a short corner.
Thomas Muller takes a shot. Victor Valdes makes a save.
Bastian Schweinsteiger produces a cross, clearance by Gerard Pique.
Philip Lahm takes a shot. Blocked by Gerard Pique. Corner taken by Arjen Robben from the right by-line played to the near post, clearance by Gerard Pique.
A cross is delivered by David Alaba, Rodriguez Pedro gets a block in.
Corner taken by Hernandez Xavi, Gerard Pique has a headed effort at goal from deep inside the area missing to the left of the target.
Inswinging corner taken from the left by-line by Franck Ribery, Gerard Pique manages to make a clearance.
David Alaba sends in a cross, blocked by da Silva Dani Alves.
Free kick awarded for a foul by Bastian Schweinsteiger on Hernandez Xavi. Sergio Busquets takes the free kick.
Unfair challenge on Hernandez Xavi by Bastian Schweinsteiger results in a free kick. Free kick taken by Hernandez Xavi.
Shot by Arjen Robben. Save made by Victor Valdes.
The ball is delivered by Philip Lahm, clearance by Gerard Pique.
The match has kicked off.
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Bayern Munich cemented their status as the growing power in European football by ruthlessly dismantling favourites Barcelona in the Champions League semi-final first leg.