Gary Holt has quit as Livingston manager after just over two years in charge.
Holt admitted he was considering his future after losing 1-0 at home to St Mirren last Saturday.
The defeat left the club tenth in the Premiership, having finished fifth last season.
Holt, 47, said he was leaving the West Lothian club with “great regret”.
“This is not a decision that I have taken lightly but feel it is the right time for me to step away,” he said.
“I am proud to say the work we have done over the past two years has resulted in great success both on and off the pitch.”
Head of football operations David Martindale and goalkeeping coach Tony Caig will take charge when Livingston play Ayr United in the League Cup on Saturday.
Martindale said: “It’s been a tough season and we are probably a victim of our own success in comparison to last season, which ultimately raised everyone’s expectations including players along with all staff at the club.
“So, when we don’t quite hit those heights again it can feel like something needs to change and I totally understand Gary’s thought process.
“Gary can leave Livingston knowing he has left us in a better place than when he arrived. Has Gary helped improve Livingston FC? That’s a simple one to answer – 100% yes.”