The Germans opened the scoring after four minutes at the Estadio da Luz in Lisbon through Thomas Mueller. But his strike was cancelled out three minutes later when David Alaba put through his own net.
But Alaba’s misery did not last long.
Ivan Perisic gave the Germans the advantage mid-way through the half. Serge Gnabry and Mueller added another two goals before the pause.
Bayern’s position of invincibility was briefly in doubt when Luis Suarez scored Barcelona’s second after 57 minutes.
Supremacy
But Joshua Kimmich’s slick finish restored the three goal advantage and Robert Lewandowski killed off any hopes of a famous comeback with Bayern’s sixth strike eight minutes from time.
Barcelona’s humiliation was exacerbated when Bayern substitute Philippe Coutinho - who is on loan from Barcelona - came off the bench to bag a brace in the closing stages.
It was the first time Barcelona had suffered a defeat by a six-goal margin since a 6-0 loss to Espanyol in 1951 and the first time the first XI had conceded eight in a competitive match since an 8-0 annihilation against Sevilla in 1946.
Uncertain future
Barcelona boss Quique Setien described the defeat as "tremendously painful". The 61-year-old added: "I am aware of what such a defeat means. I think what has happened needs to be analysed with a bit more perspective.
"The credibility of a coach is diminished when this happens, clearly. That is obvious.”
Barcelona president, Josep Maria Bartomeu, promised to take decisions in the coming days.
Speaking to the Spanish TV station Movistar Plus, Bartomeu added: "Now is not the time for decisions, it is the time to apologise to the members, the Barcelona fans, because it was not a good day for them.
"We are hurting, but once we get to next week we will start making decisions."
Performance
No such existential angst swirled around the Bayern camp after their most emphatic victory against a European powerhouse.
"I am just happy we could put in a performance like that under such pressure," said Mueller whose side will face the winners of Saturday night’s quarter-final between Mancheser City and Lyon.
"My experience is that it gets more difficult now,” added Mueller. “It starts again at 0-0 and, in a semi-final, the teams tend not to get worse, but better.
"We can go to bed with a smile and enjoy the atmosphere, but we want to stay in the tournament.”
