Liverpool signed Origi from Lille for £10m last summer before sending the striker back to the French side on loan.
He told Sky Sports News HQ: “I think Liverpool is a wonderful club that deserves to be at the top and to be honest with the players they have, with the quality they have, then they should be finishing at the top of the league.
“I’m very happy to be going there. Brendan Rodgers is a very good coach and he has proved that, so it will be very exciting to work with a world-class coach.
“Most of all it is important to be at a good club where people believe in you and where you feel good and at Liverpool I had a really good feeling and they have experience of working with young players.
“It’s always nice to play with good players. The important thing is that I work hard and then I think everything will be okay.”
Origi made 33 appearances last season and scored eight goals for Lille, including a hat-trick in a league game against Stade Rennes in March.
He is expected to win his 14th cap for Belgium in a friendly against France in Bordeaux this weekend.