Garry Monk has quit Leeds United.
Monk's agent requested that the option of a 12-month contract extension wasn't exercised.
Monk took over at Elland Road last summer and led Leeds to the brink of the playoffs.
But the season petered out as they won only two of their last 11 games, leaving them five points outside the top six.
A club statement read: "Leeds United can confirm that we have received Garry Monk's resignation from his role as First Team Manager.
"We are shocked and disappointed by Garry's decision but his resignation has been reluctantly accepted by Chairman Andrea Radrizzani.
"Andrea made it clear to the media yesterday that his intention was to exercise the Club's option to extended the Manager's contract for another 12 months and immediately begin negotiations for a longer term deal.
"Mr Radrizzani has met with Garry twice since taking over at Elland Road earlier this week and during the second meeting yesterday it became clear that Garry was considering life beyond Leeds United as at no time did Garry wish to discuss terms for a longer contract.
"Following that meeting yesterday Garry's agent requested that the option was not exercised and his resignation was received this morning.
"Whilst we are deeply saddened by Garry's decision, there is no individual bigger than our Club and we will now begin a process to identify ad appoint a new Head Coach to take the club to the next level. "We thank Garry for his contribution during his time at Leeds United, we are disappointed that would could not continue on this journey together."