Liverpool have completed a £35m deal to sign midfielder Alexis Mac Allister from Brighton on a five-year contract.
The fee could rise to £55m for the Argentina playmaker, who helped Brighton finish sixth in the Premier League this season to qualify for Europe for the first time.
The 24-year-old scored 20 goals in 112 appearances for the Seagulls and helped Argentina win the 2022 World Cup.
"It's a dream come true and I can't wait," said Mac Allister.
"I wanted to be in [from] the first day of pre-season, so it's good that everything is done. I'm looking forward to meeting my team-mates.
"It was a fantastic year for me - World Cup, what we achieved with Brighton - but now it's time to think about Liverpool and try to be a better player and a better human being every day."
Liverpool manager Jurgen Klopp is looking to reinforce his midfield with James Milner, Naby Keita and Alex Oxlade-Chamberlain all leaving Anfield this summer.
They were priced out of a move for Borussia Dortmund's England teenager Jude Bellingham, who looks set to join Real Madrid after the clubs agreed a 103m euro (£88.5m) fee.
Mac Allister joined Brighton from Argentinos Juniors in January 2019 and immediately went back to the Buenos Aires club on loan.
He has played 16 times for Argentina and emerged as a key player during their third World Cup triumph in December.
Having sat out their opening defeat by Saudi Arabia, he started the next six games and starred in the final against France.
"Since I won the World Cup, I said that I want to win more trophies and I think that this club will help me to do that," said Mac Allister.
"That's the aim and when you are in a big club like this one you have to win trophies. I can see how big this club is - the players we have, the staff, everyone. I'm really pleased and looking forward to playing for this club."
Mac Allister thanked Brighton on Instagram, writing: "It's time to say goodbye to the club that opened the doors for me and gave me such amazing moments.
"I never thought I was going to live what I have lived in these three and a half years, but this club gave me that opportunity and I'll be forever grateful.
"I don't have any doubts that this team is going to achieve many important things, because they have the football skills and human quality to do it.
"I'll always watch you and support you. Thanks a lot Seagulls, you will always have a special place in my heart!"
Source: BBC