"I am very excited to be at a big club like Liverpool and it is a dream for me," said the Israeli captain.
"I had a good time at West Ham but when a club like Liverpool shows an interest in you then you can not refuse them.
"This is the biggest move of my career and I am at a club that fights for trophies every season. I'm 27 now and I am ready for this challenge. I know the Premiership and I want to work hard in every training session, and in every match and prove myself.
"Liverpool is a massive club with great supporters and I can't wait to play my first game in a red shirt."