Leeds United announced the appointment of Paul Heckingbottom as head coach to replace Thomas Christiansen on Tuesday - less than a week after he signed a new contract at fellow Championship side Barnsley.
The 40-year-old, who had been in charge at Oakwell since February 2016, agreed new terms with Barnsley on Friday but has swapped that rolling contract for an 18-month deal with their Yorkshire rivals.
"Leeds United are delighted to confirm the appointment of Paul Heckingbottom as new head coach of the club," said a statement from the club.
"The 40-year-old has signed a contract running until the summer of 2019 and succeeds Thomas Christiansen, who left Leeds United on Sunday."
Christiansen was sacked after a 4-1 home defeat by Cardiff, a seventh straight match without a win.
Leeds began the season with a nine-game unbeaten run, raising hopes of a promotion push but they have slipped to 10th in the Championship.
Heckingbottom will be expected to swap Barnsley's relegation battle for an assault on the play-offs - Leeds are seven points behind sixth-placed Bristol City.
Barnsley said in a statement that they were "thoroughly disappointed to announce that Paul Heckingbottom has joined Leeds United".