Gary Caldwell has joined Wigan from Celtic on a four-and-a-half-year deal for an undisclosed fee, the Barclays Premier League club have confirmed.
The 27-year-old Scotland international made over 120 appearances for Celtic since joining from Hibernian in the summer of 2006.
Caldwell becomes Wigan's third signing of the January transfer window following the captures of Vladimir Stojkovic and Steven Gohouri.
Caldwell made 151 appearances in all competitions for the Hoops, scoring seven goals.
He won two Clydesdale Bank Premier League titles, one Scottish Cup and one League Cup during his three and a half years at Parkhead.
The Stirling-born former Newcastle trainee was also named 2009 SPL Player of the Year.
He described leaving Celtic as a "wrench" but was lured by the prospect of playing in the Premier League and was persuaded to move to the DW Stadium by the enthusiasm and drive of Latics boss Roberto Martinez.
"The manager made it quite clear what his ambitions are for this club and how much he wanted to bring me here," Caldwell told Wigan's official website, www.wiganlatics.co.uk.
"To play in the Premier League has always been an ambition of mine but I know how tough it's going to be to get in the side and I need to focus on winning a place and doing the best I can for my new club.
"It's a massive wrench for me to leave a club like Celtic but I want to thank the club and all the fans for the support they've given me in my time there.
"But I'm a Wigan player now and I can't wait to get started in the Premier League."