By SABC Sport
8th June 2023
The 24-year-old's arrival on a five-year contract signals the start of manager Jurgen Klopp's much-vaunted midfield rebuild which will likely see further additions made this summer.
A fee has not been disclosed but it is understood the Argentina international had a favourable release clause, which is reported to be as low as an initial £35million, inserted into the Brighton contract he only signed in October to avoid him leaving on a free at the end of the season.
"Since I won the World Cup, I said that I want to win more trophies," the midfielder told LFCTV.
"I think this club will help me to do that. That's the aim, and when you are at a big club like this one, you have to win trophies. That's what I want.
"It doesn't matter which one. Of course, every player wants to win the Champions League and the Premier League, but I will do my best to help the team and try to win every trophy."
Mac Allister was on Liverpool's radar prior to his move to the Seagulls in 2019 but the club felt his development was still in its early stages, although his versatility to play in several positions was a key factor in their interest.
He became as a priority target ahead of the World Cup in Qatar, in which he played a significant part in Argentina's victory, and Liverpool were keen to secure his services to avoid a bidding war having pulled out of the race to sign Borussia Dortmund's Real Madrid-bound midfielder Jude Bellingham when he became too expensive.
Mac Allister said he was looking forward to working with one of the best managers in the world and Klopp was equally fulsome in his praise of the player.
"We are adding a very talented, very smart, very technically skilled boy to our squad and this is super news, really it is," Klopp said.
"It is clear he is someone who can play in a number of positions in the midfield and is an all-rounder. He is calm and composed and someone with proper game intelligence.
"I'm really happy his next steps will now be with us and we get to work with a player who is already excellent and experienced, but also has so much more to come given he is just 24 years old.
"There is no pressure on him. He is still so young, so it is obvious he will only improve and our job is to help him take the next steps."
Mac Allister's age and his career appearances (160) fit in with the demographics of some of the club's most successful signings like Mohamed Salah, Virgil Van Dijk and Roberto Firmino and he represents the start of an overhaul of a midfield which lost James Milner, Naby Keita and Alex Oxlade-Chamberlain at the end of their contracts this season.
The groundwork on the deal has been going on for some time as the club have a long-standing relationship with the player's agent Juan Gemelli dating back to Philippe Coutinho's transfer from Inter Milan in 2013.
Departing sporting director Julian Ward pushed the deal to completion but has now handed over transfer business to his replacement Jorg Schmadtke.
Liverpool have also been linked with Bayern Munich's Ryan Gravenberch, Nice's Khephren Thuram, Borussia Monchengladbach's Manu Kone and Southampton's Romeo Lavia and will be looking to get the majority of their business done early in time for the start of pre-season on July 8.
Mac Allister's departure may not be the last from Brighton with Moises Caicedo, a target for Arsenal in January, attracting more interest but the Seagulls' Argentina international left with the club's best wishes.
"We are incredibly proud of Alexis and we are sad to see him go," said chairman Tony Bloom.
"He did something very special, becoming the first Brighton and Hove Albion player to win the World Cup, and was a key player in our best-ever season."