Celtic produced arguably their greatest win since beating Inter Milan 2-1 to lift the European Cup in 1967 as they stunned tournament favourites Barcelona 2-1 in Champions League Group G at Celtic Park.
The Scottish champions - who are celebrating their 125th birthday this week after being founded by an Irish priest in 1887 and playing their first game a year later - produced an almighty defensive effort in front of 60,000 fans to snuff out Barca's fabled stars and were rewarded with a couple of clinical goals, one in each half.
Kenyan midfielder Victor Wanyama, who at 21 is one of the most promising midfielders in the tournament, powered home a header from Charlie Mulgrew's corner on 21 minutes to give Neil Lennon's young side the lead before 18-year-old substitute Tony Watt - making his debut for the Glasgow side in the competition - pounced on some loose play by Barca captain Xavi to bound away before thumping the ball beyond Victor Valdes on 83 minutes.
Lionel Messi netted a consolation for Tito Vilanova's team a minute into stoppage time, but Celtic clung on for the final three minutes for the win with all their players almost out on their feet after such an exacting evening.
It was the perfect response from Celtic after they had suffered the agony of a 2-1 defeat to Barcelona deep into stoppage time at the Camp Nou a fortnight ago. Celtic and Real Madrid are the only teams to beat Barcelona this season.
The result gives Celtic a glorious chance of reaching the last 16 of the tournament. They remain second in the section two points behind Barca, who need a point at Spartak Moscow on November 20 to qualify.
Celtic will qualify if they overcome Benfica - who completed a 2-0 win over Spartak in the night's other group match - in Lisbon on the same night in their next group match, but a draw would be good enough with Spartak due at Celtic Park in the last round of group matches next month. Three more points at home might well be enough to see Celtic through to the knock-out stages.
Barcelona had lost just one of their last 21 Champions League games, winning 16 matches, drawing four and losing one game. They were also the only team to have beaten Celtic at Celtic Park in the Champions League, winning 3-1 in the group phase in 2004 and 3-2 in the last 16 in 2008.
Celtic went into the match hindered by the absence of captain Scott Brown due to a virus, but set about their task with considerable relish as they let Barca play in front of them before hitting on the break aided by the languid stride of Georgios Samaras to carry the ball up the park.
The performance, with Wanyama, goalkeeper Fraser Forster, Watt and right-back Adam Matthews very much to the fore, brought lifelong supporter and pop star Rod Stewart to tears. It was little wonder as Celtic shed blood, sweat and tears to complete a fabulous win that had to be seen to be believed.
Claims of anti-football were also dispelled with Celtic playing with two strikers. Barcelona, with Dani Alves and Jordi Alba flying up and down the flanks as per usual, dominated possession as they usually do, but their best efforts of the first half were met by an utterly unflinching wall of green-and-white hooped shirts.
Somehow Celtic had bridged the gap in finance, glamour and quality between the Scottish Premier League and La Liga with their obvious desire not to buckle. When a home player was not in front of the ball, English goalkeeper Forster was on hand to produce another towering display after he excelled in Barcelona.
He clasped an effort from Alexis Sanchez on seven minutes before nudging a Messi shot onto his bar and over on 29 minutes when the net looked likely to be the only thing to halt the ball.
Celtic needed good fortune to remain ahead after Wanyama's opening goal when Alexis saw a header come back off a post and spin wide after some terrific play by the always dangerous Alves to deliver an eye-catching cross.
Celtic were relieved to scramble to half-time holding the lead having conceded in the final minute of the first half in Barcelona a fortnight ago.
Messi saw Forster claw out a couple of probing efforts while the goalkeeper raced from his line to prevent a shot from Alexis finding the net.
Celtic also had their moments in the second period. Marc Bartra denied Mulgrew a certain second when he raced back to make a telling block.
Alex Song should have been sent off on 69 minutes after taking out Miku with a cynical late challenge having earlier being booked. It was little surprise to see him replaced by Cesc Fabregas for the closing 20 minutes.
Javier Mascherano could also have walked when he seemed to pull back Watt as the youngster appeared poised to score his second of the night having struck moments earlier.
Kelvin Wilson did superbly well to block a header from Pedro with Celtic leading 2-0 before Forster was finally beaten when Messi reacted quickest to score after Pedro had saw Forster dive low to his left to claw out a shot.
In the end, it didn't matter as the home fans celebrated in the rain as another teeming European night at Celtic Park broke into a party amid scenes of bedlam.
MAN OF THE MATCH
Fraser Forster - Celtic: Another superb performance from the goalkeeper to deny Barcelona. Probably deserved a clean sheet for his performance.
CELTIC: Forster 9, Lustig 7, Ambrose 8, Wilson 8, Matthews 8; Commons 7, Wanyama 9, Ledley 7, Mulgrew 7; Miku 7, Samaras 7. Subs: Kayal 6, Watt 8.
BARCELONA: Valdés 6, Alves 7, Bartra 5, Mascherano 5, Alba 7, Xavi 5, Song 5, Iniesta 7, Alexis 6, Messi 6, Pedro 6. Subs: Piqué 6, Fàbregas 6, Villa 6.