Gary Caldwell has joined Wigan from Celtic on a four-and-a-half-year deal, the Premier League club have announced on their website.
The 27-year-old wanted to quit the Glasgow giants and had looked set to join forces with former boss Gordon Strachan at Middlesbrough. However, Caldwell performed a U-turn and opted for Roberto Martinez's side instead.
Martinez said: "Gary is a leader and he is exactly the right character we need at the club. He is a winner and will become a huge asset for Wigan Athletic. He is a commanding defender who will lead by example on and off the pitch.
"He has been part of a winning team at Celtic and brings with him great experience, having won league titles and cups, and played in the Champions League. I am excited to welcome him on board at Wigan Athletic."
Caldwell added: "The manager made it quite clear what his ambitions are for this club and how much he wanted to bring me here.
"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 Athletic player now and I can't wait to get started in the Premier League."
Wigan chairman Dave Whelan told the Scottish Daily Mail: ''We knew the lad was keen to work again with Gordon Strachan at Middlesbrough but we wanted him to come here and made him a very good offer.
''You always think a player will fancy a crack at the English Premier League rather than the Championship.''
Caldwell becomes Wigan's third signing of the January transfer window following the captures of Vladimir Stojkovic and Steven Gohouri.