Serbia Under-21 midfielder Marko Grujic has completed his transfer from Red Star Belgrade to Liverpool.
Grujic put pen to paper on a deal with the Premier League club on Wednesday, but will return to Red Star on loan for the rest of the season.
Liverpool did not confirm how much they have paid for the 19-year-old, who becomes Jurgen Klopp's first new signing, but Red Star announced before Christmas that the fee was EUR7million.
Speaking to his new club's official website, Grujic said: "I'm very excited and so proud to be here and a member of Liverpool Football Club. I can't wait to get started, play at Anfield and train at Melwood.
"I was thinking about my progress in my next period and decided it was good for me to come here and try to be the best I can.
"I want to play in front of one of the loudest set of fans in Europe at Anfield.
"I also like the atmospheres at other stadiums, the crowds are very good. I like to play under pressure and that's why I've come here - because it brings out the best in me."
Klopp added: "We're very pleased because Marko is a big talent and we've seen him a lot of times.
"When I came here, our scouts showed me some footage of a very skilled player from Red Star Belgrade. We watched it, we spoke to him, we met each other - he's a good boy, a young boy but plays an important role at the moment at Red Star, who are the best team in Serbia.
"To describe him, I would say he's a tall boy, but quick and good at technical things. He can play passes and can dribble. But he is young, so he has to develop. He will do this, so everything is okay."