Club acquired Wales national team midfielder Joe Allen for 19 million euros.
The 22-year-old footballer wore Swansea shirts last season and became Liverpool's second purchase this summer after Italian Fabio Borini.
"I feel incredible. Everyone knows the history and achievements of this club, so I am extremely happy," said Allen. "I want to be part of the passion for which these people are famous. I hope we have successful years ahead."
Last season, Allen was trained by Brendan Rodgers, who also moved to Liverpool this summer. He was delighted that the team would have a former pupil who played an important role in his passing-based tactical scheme.
"I am very pleased with his decision. Joe will fit in well with the team, and I am particularly impressed by his ability to control the game," Rodgers said.
Last season, Allen scored four goals in 36 matches in the English championship.