Roared on relentlessly by their fans, the Reds produced an incredible all-action display to claw back and then ultimately overturn their 3-0 deficit from the Nou Camp with an unanswered four-goal salvo in thrilling style.
It is the first time since 1986 – when Barcelona knocked out Gothenburg in the old European Cup – that a team have recovered a three-goal first-leg deficit to win a semi-final in this competition.
Divock Origi started the unlikely revival, tapping home from close range after seven minutes, but it was only when substitute Georginio Wijnaldum scored twice in the space of 122 seconds after the break that the tie truly swung in Liverpool’s favour.
Barcelona were rattled, and even Lionel Messi was unable to steady the ship before Origi struck again with the goal that would decide the tie on aggregate, after Trent Alexander-Arnold caught the visitors’ defence napping from a corner.
By now Anfield was rocking and the home fans stayed on their feet to cheer their side home in the closing minutes, with a shell-shocked Barca side unable to fashion any serious response.
The final whistle brought delirious celebrations on the pitch and in the stands, where the Reds supporters had played their part in an unforgettable match.
Liverpool have managed famous European fightbacks before, notably when they won this competition for the fifth time in Istanbul in 2005, but this was arguably the greatest in their glittering history.
They will go for a sixth triumph in Madrid on 1 June, where they will meet either Ajax or Tottenham in the final.
Press, harry, hassle – Barca outfought by Liverpool
Few people gave Liverpool any hope after the size of their defeat in Spain last week, especially with Mohamed Salah and Roberto Firmino out injured.
But Reds boss Jurgen Klopp urged his players to keep believing, and masterminded an extraordinary performance and result.
Origi and Wijnaldum, who replaced the injured Andy Robertson at half-time, provided the goals but Liverpool had heroes all over the pitch.
Just as Klopp promised before the game, Liverpool did not stop – maintaining an astonishing tempo to press, harry and hassle their illustrious visitors, and ultimately defeat them.
The Barca defence struggled to deal with Origi’s physical presence throughout and it was the big Belgian who supplied the first goal, firing home after Marc-Andre ter Stegen failed to hold Jordan Henderson’s shot.
More pressure followed but Barca held out until after half-time, when Wijnaldum burst into the box to meet Trent Alexander Arnold’s low cross and hammer his shot home.
Moments later, Liverpool were level on aggregate. This time it was Xherdan Shaqiri who provided the cross for Wijnaldum to rise and head home.
Barca were buckling under the pressure and they could not hold out. Liverpool sealed a famous victory 11 minutes from time when Alexander-Arnold feigned to leave a corner but instead took it quickly, finding Origi unmarked to sweep the ball home.
Deja vu for Barcelona
Barca have been here before, being beaten 3-0 by Roma in the quarter-finals last year to go out after winning the first leg 4-1, and their wait for a first final since 2015 continues.
They were comprehensively out-fought and out-thought here, and although they did have chances they cannot argue they deserved anything but a defeat.
There was only a brief spell in the first half when La Liga’s champions threatened to find their rhythm but, in the space of five minutes, Alisson denied Messi and Philippe Coutinho, and Jordi Alba inexplicably chose to pass the ball with only the Liverpool keeper to beat.
Messi, so electric a week ago, would go on to have a rare night to forget – especially in the second half when Wijnaldum’s goals put the tie back in the balance.
Suarez too, was anonymous, with his only notable role coming as the pantomime villain as he was booed relentlessly by the fans who used to worship him.
He had his side’s best opportunity of the second half, when Messi slid him clear with the score still 1-0 on the night, but Alisson was alert and that was pretty much the last time the visitors threatened.
The 122 seconds that turned the tie around
Liverpool join exclusive club – the stats
Liverpool will seek another success against the odds when they return to Premier League action on Sunday. They host Wolves in their final game of the season (15:00 BST) hoping results go their way to turn around a one-point deficit and take the title from Manchester City, who are at Brighton.
Source: BBC SPORTS