Leeds United have signed Chesterfield defender Liam Cooper for an undisclosed fee on a three-year contract.
The Championship side re-opened talks for the 22-year-old this week after having two bids rejected in July.
Cooper joined the Spireites from Hull City in January 2013, and last season made 48 appearances in all competitions as they won the League Two title.
"Liam has lots of potential and a great left foot. It's great business," said Leeds boss Dave Hockaday.