Nawrocki made 30 appearances, all but four of them starts, for the Polish Ekstraklasa runners-up last season, scoring four goals.

Celtic manager Brendan Rodgers described him as "a very highly-rated young player and someone who we believe will be a great addition to the squad".

"He's also a player I am very much aware of, having seen him play for Legia Warsaw in the Europa League and I know he was very keen to move to Celtic," he told his club website.

The Bremen-born defender came through Werder Bremen youth ranks and transferred to Legia Warsaw permanently last summer after a year on loan.

Nawrocki helped Legia win the Polish Cup last season, scoring the deciding penalty kick as Legia defeated league champions Rakow Czestochowa 6-5 in the shootout that followed a 0-0 draw.

The Poland Under-21 international was a substitute as Legia repeated the feat after another goalless draw with Rakow in this season's Polish Super Cup.

However, he did not feature in Friday's win over LKS Lodz at the start of the domestic league campaign.

Nawrocki pointed out that he knew "how big this club is" considering the number of Polish players who have previously played for Celtic.