Speaking to the club media, Jurgen Klopp said: "We are adding a very talented, very smart, very technically skilled boy to our squad and this is super news. I don't think the football world needs me to say too much about his qualities.
"They are already pretty well known but it is clear that he is someone who can play in a number of positions in the midfield and is an all-rounder, I would say. Alexis is calm and composed and someone with proper game intelligence.
"Of course, he is a player we have known about for a long time and I have watched him grow from a young boy coming into the Premier League to a man who helped his country win the World Cup. That is quite a journey.
"And I'm really happy Alexis' next steps will now be with us and we get to work with a player who is already excellent and experienced in the Premier League, but also has so much more to come given he is just 24 years old."