“I am very happy and delighted a club as big as Liverpool showed interest in me. I’m very excited,” Origi told the Liverpool website.
“I know it’s a club with a great history, great fans and a lot of great players. For me, Liverpool is one of the greatest clubs in the world and I’m very excited to be part of this great history.”
Origi travelled to the United States, where Liverpool are on a pre-season tour, in order to complete the deal. Liverpool did not disclose the length of his contract.
After a breakthrough campaign with Lille in 2013-14, Origi impressed for Belgium at the World Cup, scoring an 88th-minute winner against Russia in the group phase to send his team into the last 16.
Origi is Liverpool’s fifth close-season signing, following the arrivals of the former Southampton trio of Adam Lallana, Rickie Lambert, and Dejan Lovren, and German midfielder Emre Can from Bayer Leverkusen.
While the teenager will have to wait at least a year before making his Liverpool debut, he is already excited about the prospect of becoming a part of manager Brendan Rodgers’s side.
“The fact we have a young team and can grow is the most exciting part,” he said.
“With the coach we have, he’s a great manager who can handle a young team. He’s said a lot of good things about Liverpool and told me it’s the perfect club for me.
“This year I’ll have a chance to play at European level, in the Europa League or Champions League.”
Liverpool narrowly lost out to Manchester City in the battle for last season’s Premier League title.
They start the 2014-15 season at home to Southampton on August 17.