Celtic have signed Jaroslaw Fojut from Polish league-leaders Slask Wroclaw on a pre-contract agreement.
The 24-year-old defender has agreed a three-year deal with the Scottish Premier League leaders that will commence from the summer.
Fojut spent five years at Bolton from 2004 to 2009, making one appearance.
"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.
Lennon, speaking to the club website, said he has been aware of Fojut for some time.
"I actually played against him when he was on loan at Luton for Nottingham Forest and often wondered what happened to him, as he was on loan from Bolton at the time and I was really impressed by him," he added.
"So (Celtic scout) John Park and myself got talking, and his name came up again.
"We did a bit of homework on him since then, and I think he's been in excellent form for his club this year and on the verge of international recognition.
"To get him on a pre-contract is a good bit of business again for the club.
"He's strong, technically good, quick, and he's very good in the air.
"At 24, he's at a good age. He had a bad injury and was out of football for around a year, but it looks like he's come back stronger than ever, and I'm pleased with the signing.
"I think his all-round game is very good. He has been playing at a decent level of football from a young age, but what I like about him is his physical qualities."