Celtic have signed Jaroslaw Fojut from Polish league-leaders Slask Wroclaw on a pre-contract agreement starting from the summer.
The 24-year-old defender, who made one appearance for Bolton between 2004 and 2009, has agreed a three-year deal with the Scottish Premier League leaders.
“He already knows the British game, so I don’t think it will take him too long to adapt to the rigours of Scottish football,” said manager Neil Lennon.
He added: “I actually played against him when he was on loan at Luton for Nottingham Forest and often wondered what happened to him. He was on loan from Bolton at the time and I was really impressed by him.”
Meanwhile, 20-year-old defender Josh Thompson, who has made 21 first-team appearances for Celtic since joining from Stockport in 2009, has signed for Chesterfield on loan until the end of the season.
Thompson moved to Peterborough United on a season-long loan in August but he was allowed to leave London Road after failing to break into the team.