Liverpool have signed Thiago Alcantara from Bayern Munich in a deal that could rise to £25m.
Liverpool will pay £20m for the Spain international, with the potential for a further £5m in add-ons, and the midfielder will wear the No 6 jersey.
Thiago arrived in the UK on Friday morning, flying in to Manchester from Munich to complete a medical and finalise the deal.
The 29-year-old helped Bayern win the treble last season, as they beat Paris Saint-Germain in the Champions League final last month in Lisbon.
"I think it's an amazing feeling. I was waiting for this moment for a long time and I am very, very happy to be here," Thiago told Liverpool's official website.
"When the years are passing, you are trying to win as much as you can - and when you win, you want to win more. I think this club describes what I am as well; I want to achieve all of the goals, win as many trophies as possible.
"It also [has] this kind of family [feeling] that I need because we [like to] have a very close relationship with the club and I think I will feel this, I will have this feeling, with this club as well.
"I must adapt to the team as fast as I can in the situation and the context that we are living right now.
"Everything is more compact and we started a little bit later, but still it is football and I think we have to mix all the big things up, all the good things we have. I will help the team in a defensive and offensive [way] and also in a mental aspect.
"[The fans] are not more excited than I am - for sure not! It is not about saying words, it is about doing the things. I will give my heart on the field to my team-mates, the club and also to the fans."
'Most difficult decision of my sports career'
When he left the Bundesliga club, Thiago took to social media to post a goodbye video which said: "I have made the most difficult decision of my sports career.
"I will close this chapter in this wonderful football club where I have grown as a player for seven years.
"Triumphs, joys and also hard times but what I am most proud of is that I arrived in Munich as a young man full of dreams and now I will leave completely fulfilled with the club, a history and a culture.
"Here I learned to love a tradition that I am now saying goodbye to but which I will never forget.
"My decision is purely a sporting nature as a soccer player, I want new challenges to develop myself further. Bavaria will always be my home, thank you FC Bayern."
Bayern boss Hansi Flick paid tribute to Thiago on Thursday, saying: "Thiago is an exceptional player who spent seven hugely successful years here.
"He's a wonderful person and an outstanding professional. It was very emotional today when he said goodbye to us all."
Thiago started his career at Barcelona and was handed his debut for the Catalan side by Pep Guardiola in 2009 at the age of 18.
He was an unused substitute as Barca beat Manchester United in the Champions League final the following season.
Thiago joined up with Guardiola again in 2013 when the then-Bayern boss took him to Bavaria. He went on to win seven Bundesliga titles and four DFB-Pokal cups.
Analysis: Thiago signing shows how high Liverpool are regarded
Sky Sports News reporter Kaveh Solhekol told The Transfer Show:
"Liverpool signing Thiago shows how high Liverpool's standing is right now in world football because this is a player who is the best in the world at what he does. He's been at Bayern Munich for seven seasons, he's won a title every season, he's just won the Champions League and was one of the best players in the competition last season.
"Bayern were aware his contract was running out next summer. They put a new contract in front of him, a four-year deal and they thought it was all agreed, he was going to sign on the dotted line but at the last minute, he had a change of heart and decided to leave this summer. Bayern decided to let him go and he wants a new challenge which is at Liverpool.
"From Liverpool's point of view, Bayern were initially asking for €30m and there was no way Liverpool were going to pay that. The way they have structured this deal is that they are paying £20m but over four seasons so £5m per year for Thiago. When you look at it like that, it is the best lease purchase deal I have ever seen to get a player that good for just £5m per year.
"That's why a lot of Liverpool fans on social media are saying their sporting director Michael Edwards is a genius."
'Thiago deal a no-brainer for Liverpool'
Sky Sports News reporter Vinny O'Connor:
"Liverpool's stance throughout the summer was that they would not be signing Thiago Alcantara - that changed a little a couple of weeks ago when the suggestion was they would only try to sign him if someone was leaving, but they did not believe that was going to happen.
"Now Liverpool have decided to go ahead regardless of that and they think Thiago is the man for them.
"Jurgen Klopp had also been consistent throughout the summer - Liverpool would not be doing business unless a really good opportunity presented itself and a deal was there to be done.
"This is a deal that Liverpool could not turn down.
"At 29, Thiago does not necessarily fit the FSG [Fenway Sports Group, Liverpool's owners] model of buying players young, coaching them and increasing their ability and value, but the out-and-out quality of Thiago, combined with his experience of performing on the biggest stage, meant this particular move was a no-brainer.
"He is a player for the here and now, untested in the Premier League but someone who is used to performing on the biggest stage for Barcelona, Bayern and Spain.
"The signing should also help to solve an issue that Liverpool have recognised recently - Trent Alexander Arnold alluded to it in an interview a couple of weeks ago - the game plan needs to change.
"It has been in the back of Liverpool's minds to change the dynamic in midfield. It is not a case of things going stale but they are keen to give the opposition something else to think about now. Liverpool have been playing the same way for a couple of years and Thiago brings them something completely different.
"The signing of Bayern Munich's treble-winning midfielder renews that competition for places and says to the other players in that position they have to raise their game again.
"They have now decided to move from a position of strength to freshen things up and give other teams something new to think about."
Sky Sports' Adam Bate:
The commentator was just saying how comfortable Paris Saint-Germain were looking when it happened. "They are quite happy for Bayern to have the ball in their half," he said. But it was at that precise moment that Thiago Alcantara weaved his magic, firing a crisp pass between the lines.
The ball was in the back of the net seconds later. The goal was enough to win the 2020 Champions League for Bayern Munich and while scorer Kingsley Coman was the official man of the match, the role of Thiago in the team's triumph escaped no one.
At 29 and reluctant to sign a new contract, Bayern realised they might have to sell. Liverpool have pounced and it is easy to see why. Jurgen Klopp's side can do almost anything. But they cannot do what Thiago can do…
Analysis: A staggering CV and pedigree
Sky Sports' Adam Smith:
His CV tells the story. At 29 years old, Thiago has racked up 11 league titles with Barcelona and Bayern Munich. Since his league debut, he has only ever missed out on the domestic crown once - back in 2011/12.
If that was not enough, what else interested Jurgen Klopp? The reduced fee from his dwindling contract was undoubtedly attractive, but so too are his strengths - in particular, his ability to press opponents.
Thiago played only 106 minutes in the Bundesliga after the restart due to a groin injury
Only Wolfsburg's Maximilian Arnold reclaimed possession in the middle third more than Thiago in the Bundesliga last season - and he played 1,055 minutes more than the Spain international.
Thiago also offers an improved dimension to Liverpool's existing midfield tranche: the ability to run with the ball. His frequency of completed dribbles is outstanding, given the fact he patrols central areas of the pitch.
In addition, the 29-year-old retains possession, despite his forward-thinking drive and above-average number of passes attempted - clocking a passing accuracy of 90.5 per cent, which ranks 21st in the league.
Thiago provides unrivalled pedigree, with 12 years' experience at powerhouse clubs and nine with Spain, while fitting the mould for a midfielder under Klopp.
Summer transfer window - key dates and times
The summer transfer window will close at 11pm on October 5.
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