Match report as Liverpool score three goals in 12 second-half minutes to book third Champions League final berth in five years against either Real Madrid or Man City in Paris; Villarreal had wiped out first-leg deficit before fading in El Madrigal
Liverpool overcame a valiant performance by Villarreal to book a third Champions League final in five seasons with a 3-2 victory at El Madrigal to complete a 5-2 aggregate win on Tuesday night.
The six-time European champions saw their first-leg advantage extinguished in the first half as Boulaye Dia's third-minute opener was added to by Francis Coquelin, who outjumped Trent Alexander-Arnold to float a header into the top corner (41).
But Fabinho restored Liverpool's advantage in the tie when his near-post shot flashed through Geronimo Rulli (62). It turned the tide as the inspired substitute Luis Diaz restored the visitors' two-goal cushion from Alexander-Arnold's cross (67).
It was a very dominant second-half display from Jurgen Klopp's side, who capitalised on further dubious goalkeeping as Sadio Mane nipped in front of the roaming Rulli, rode the challenge of Juan Foyth to stroke into an unguarded net (74).
There was still time for Etienne Capoue to be sent off in the final five minutes following a second bookable offence on Curtis Jones as Liverpool march onto the Paris showpiece in 25 days' time, where an unprecedented quadruple might await.
Emery true to his word as Reds made to suffer
This was the epitome of a game of two halves. It will be viewed as a missed opportunity in Spain for Villarreal after an opening 45 minutes in which Unai Emery was true to his word and Liverpool duly suffered. The hosts embarked on a walk of honour at the final whistle with the city proud of a team dwarfed by the resources of their opponents.
"We never make these Champions League semi-finals easy for ourselves," Alexander-Arnold told BT Sport. "Thinking back to Roma away and Barcelona at home and now here. It was very difficult and they played very well in the first half. But we regrouped at half-time and did what we needed to do."
For all their struggles in this enthralling second leg, Klopp's side - in the midst of a defining month in their season and indeed their history - are potentially just 90 minutes away from a seventh European Cup.
The Estadio de la Ceramica had been battered by torrential rain throughout Tuesday, and the aptly named Yellow Submarine showed early signs of derailing Liverpool's quest for the greatest of achievements.
The conditions proved a leveller as the hosts were given plenty of encouragement by halving the deficit.
Pervis Estupinan was afforded too much time by Naby Keita to cross from the left, and after Capoue had ghosted around the back of Andrew Robertson, Virgil van Dijk was caught flat-footed as Dia pounced to tuck home the former Tottenham midfielder's miscue for his first Champions League goal.
On a night of fine margins, Liverpool needed to look after the ball better but a slack header by Keita enabled Gerard Moreno to feed Giovani Lo Celso only for the Argentine to run into Alisson, who got the ball first with referee Danny Makkelie waving away penalty claims.
It would only prove a short reprieve as Villarreal would level the tie before the interval as Pau Torres' long diagonal was collected by Capoue and despite the attentions of Robertson, a cute turn and cross found Coquelin rising above Alexander-Arnold at the far post to glance home a sensational second.
Liverpool needed to come out fighting in the second period having had three touches in the Villarreal penalty area for their lowest first-half total in all competitions this season.
Swapping game-changer Diaz for Diogo Jota for the start of the second half made an immediate improvement, allowing Mane to play centrally, where he has done well recently.
Alexander-Arnold very nearly re-established Liverpool's advantage when his strike from distance following a quick free-kick looped off Coquelin and clipped the crossbar.
Two minutes later, Alexander-Arnold was again involved as he found Mane in space down the right but Diaz was unable to connect cleanly with a scissor-kick from the ensuing cross.
Villarreal looked like they had expended all their energy and with Liverpool's next attack, they nudged ahead to land a huge psychological blow. Capoue committed himself to challenging Salah, who observed the space in behind to feed Fabinho. The error-prone Rulli anticipated a cross to create space at his near post but the Brazilian would blast through the goalkeeper's legs.
Liverpool fans could finally smile and after Diaz had seen a shot deflect just wide, the Colombian restored his side's two-goal lead in the tie as his downward header from Alexander-Arnold's cross again went through the legs of Rulli.
It was now one-way traffic and after another poor error of judgement from Rulli, Mane kept his composure to end any hopes of a second dramatic comeback as he latched onto a long ball to slide home his 15th Champions League knockout goal.
The win stretches Liverpool's unbeaten run to 13 games in all competitions. A 43rd success of the season extends a club record for most victories in a campaign. Liverpool look a team of destiny even when not at their best - is there anyone who can stop them?
Van Dijk: We had to dig deep
Virgil van Dijk speaking to BT Sport:
"[It was] hard work. The first half we should forget as soon as possible. Our aggression on the ball wasn't good enough. The early goal doesn't help us and helps them massively so we had to dig deep.
"We had to be very mature and obviously second half we played outstanding. On the ball, without the ball, winning the ball back as quickly as possible and then it's going to be difficult for them to keep up with the press and the runs.
"It was a well deserved win based on the second half. First half, of course, it could've been different."
Asked what Klopp said at half-time, he said: "Play football. Play the Liverpool way, how we've basically played all season.
"Get on the ball, have a lot of movements behind their high line. With the speed we have, we had to mix it up. But also, you have to show how much you really want to go to the final, that's how it starts. Second half we dominated and played so well."
What Klopp said at half-time...
Jurgen Klopp speaking to BT Sport:
"It feels like the first final in 20 years! It's outstanding. We obviously made it pretty tricky for ourselves but we knew before that these kind of things can happen. Life is always about how you can react when things don't go your way.
"Getting the first goal after two or three minutes, that's the opposite of what you want. Respect to Villarreal. Stadium, team, coach. Unbelievable. They put us under pressure man-to-man all over the pitch and we didn't play football at all.
"I told the boys, 'Yes, they have momentum, but they don't own it. With one situation we can get it back. We have to play in the right spaces and we have to force ourselves to start playing football.'
"All of a sudden, we broke the lines and found Naby and Trent in the half-spaces and we were in the game, we scored goals and we made it happen."
Analysis: Liverpool wrestle control on unruly night
Sky Sports' Ben Grounds:
It is a good time to be a Liverpool fan, who can look forward to two more finals this season. Indeed, Klopp has guided them into an eighth final during his time as manager and they are just six games away now from an historic quadruple.
Liverpool came here to complete the job, show professionalism and to finish what they started a week ago in the face of a crackling atmosphere - but they showed signs of frailty in the opening 45 minutes.
Experience would eventually tell, aided and abetted by a distinctly ordinary goalkeeping performance from the hosts' Geronimo Rulli.
Liverpool had been in this position twice before under Klopp, progressing on both occasions before losing the 2018 final to Real Madrid and winning a sixth European Cup against Tottenham the following year.
Only one team has ever overturned a two-goal deficit from a Champions League semi-final - Klopp's Liverpool against Barcelona that season. Their know-how, particularly in 2019, certainly helped here in spite of Emery's own very proud knockout history in European competition.
He was the PSG manager on the receiving end of Barcelona's infamous 'Remontada' in 2017 - and was described as the "king of the cups" by Klopp - but this proved a step too far even for him to mastermind his own turnaround for a team currently seventh in La Liga.
Ending May with four trophies in the cabinet is becoming an increasing possibility for Liverpool. The Carabao Cup was secured in February, and they can also look forward to an FA Cup final in just under a fortnight's time; underlying all of that is another epic title race which is set to go right down to the wire with Manchester City only one point ahead with four matches.
The relentless pursuit of a quadruple - and a seventh European Cup - rolls on.
Liverpool's hectic schedule continues as they host Tottenham in the Premier League on Saturday at 7.45pm knowing they cannot afford to slip up if they are to catch Manchester City.
The Champions League final takes place on May 28 at Saint-Denis's Stade de France in Paris, against either Real Madrid or Manchester City