The 24-year old defender has joined Forest on an initial one-year deal but will then begin a pre-agreed two-year contract at the end of the 2013-14 campaign.
"We are very pleased to welcome Jack to the club,” said Forest boss Billy Davies.
"He has for some time been recognised as one of the brightest defensive prospects outside the Premier League and I am delighted that we have been able to bring him in.
"To target players of his calibre is easy; the difficult part is making the deal happen.
"Not only do signings like this further signal our intentions this season, but they also highlight the hard work that is going on behind the scenes to ensure we are a force to be reckoned with.
"Things are slowly falling into place. There is still a lot of work to be done, but Jack is another piece in the jigsaw."