Liverpool completed the £8.5 million ($13.4 million) signing of Philippe Coutinho from Inter Milan.
The 20-year-old Brazilian has signed a long-term deal, the Premier League club announced, after completing his medical and acquiring a work permit, which was the final hurdle in the process.
Coutinho, an attacking midfielder, has appeared only once for his country over two years ago but has played internationally from under-17 level.
Coutinho becomes manager Brendan Rodgers' second signing of the January transfer window having already brought in Daniel Sturridge from Chelsea for £12 million ($18.9 million).
"I'm feeling very happy, it's a very important step in my career and I'm expecting to come here and play good football to give my contribution on the pitch," he said. "Liverpool is a great club with great players. We've always heard about Liverpool's history in Brazil.
"They are the club that have been interested in me and that have showed this interest so I know they believe in me and my football."