It was the visitors' heaviest defeat in Europe since they lost 5-0 away to Artmedia in 2005 and in truth it could have been more damaging.
The Hoops, with three points from their first five fixtures, were guaranteed to finish bottom of Group H before the trip to Catalonia and they found themselves behind after only seven minutes when Barca defender Gerard Pique opened the scoring from close range.
Barcelona, who needed a point to finish top of the section, were in scintillating form and when Pedro Rodriguez and Neymar added a second and third before the break a thrashing was on the cards.
Neymar scored his second two minutes after the break before grabbing his hat-trick before the hour mark as the Hoops all but crumbled.
Substitute Cristian Tello got in on the act in the 71st minute when his drive was heavily deflected past Fraser Forster by Parkhead defender Virgil van Dijk for number six before Georgios Samaras grabbed a late goal.
The Scottish Premiership leaders will surely retain their title and get another tilt at European football's elite club competition again next year.
However, they will no doubt find that the step up from domestic football will be no easier.
Celtic went into the match on the back of two fine performances, a 7-0 win over Hearts at Tynecastle and 5-0 victory over Motherwell at Fir Park but this time they got a taste of their own medicine.
Manager Neil Lennon made some bold changes to his starting line-up. Top scorer Kris Commons, with seven goals in his last four games, and stalwart Charlie Mulgrew, and striker Anthony Stokes, were dropped to the bench as defender Adam Matthews returned after a 10-game absence following shoulder surgery.
Skipper Scott Brown, who had missed the last three European games through suspension, was back in midfield trying to support Teemu Pukki
However, any Hoops' line-up would have struggled with Barca, who had a host of familiar star names including captain Xavi Hernandez, Sergio Busquets and Brazilian forward Neymar, looking for his first Champions League goal, in their line-up.
As expected the home side dominated possession from the start, with Joe Ledley and Matthews both putting Celtic under pressure with some slack passing.
In the fifth minute a timely Van Dijk tackle prevented Neymar's shot from 12 yards testing Forster with the corner coming to nothing, although the goal was only seconds away when the Hoops defence was exposed again.
Alexis Sanchez's low drive was deflected by Parkhead stopper Efe Ambrose on to Forster's legs but Pique was in the right place four yards out to knock the ball into the net.
Thereafter, Barca's dominance was at times mesmeric as they moved the Celtic players around the pitch with ease.
In the 26th minute Pique almost got a second when Xavi's deep free-kick from the right arrived at the back post but his shot from five yards was blocked by the foot of Ambrose.
At times the home side, inspired by the wonderful talent of Alexis Sanchez, were guilty of over-playing but in the 40th minute Neymar skipped past Ambrose inside the box and cut the ball back for Pedro Rodriguez to steer it low past Forster from six yards.
Things went from bad to worse for Celtic.
On the stroke of half-time Alexis Sanchez cleverly dinked the ball over the Celtic defence for right-back Martin Montoya to set Neymar up for an easy third.
Mulgrew replaced Pukki for the start of the second half but within two minutes Neymar played a one-two with Xavi and slammed the ball high into the net from 16 yards before Van Dijk could intervene.
The Parkhead side were heading for a thrashing and they could do little about it.
Neymar got his hat-trick in the 57th minute when he took a pass from Adriano, put the ball through the legs of Ambrose and slipped the ball past Forster with Matthews unable to clear.
The Brazilian should have made it six when he evaded the Hoops defence with time and space to go round Forster but Pedro Rodriguez took the ball off his toes and blasted a shot off Van Dijk and over the bar.
Still Barca drove forward, relentlessly.
Tello had replaced Alexis Sanchez and when his shot came off Van Dijk and wrong-footed Forster for the sixth, Celtic looked on the verge of total capitulation and only a block from Forster moments later denied Neymar another goal.
A bedraggled Celtic side - and their small band of supporters high up in the Nou Camp stands - had little consolation when Samaras headed in a Mulgrew free-kick in the 87th minute and he might have grabbed a second moments later, but by then it was far too little too late.