Liverpool made the announcement in a statement via the club’s official website on Monday night.
Reacting, Tsimikas told the club’s official website: “I am very happy, I am very proud to be here. For me, it is the biggest club in the world, and it is an honour to be here, and I’ll give my best.
“I want to achieve our goals. To win the league again and also to win the Champions League.”
Tsimikas has three caps with Greece national team.
He made his senior debut for Olympiacos in December 2015 and went on to make 86 appearances for the Greek side in all competitions.
