David Sissling has been the top boss in the Welsh NHS since 2011. During his time as Chief Executive the Welsh NHS has faced some of its biggest challenges in its 65 year history. Waiting lists have gone up, budgets have been under strain and senior doctors have warned of a system in meltdown.
He's also overseen some big changes in the system - including the issue of reorganising hospitals in Wales for the 21st century.
He leaves in March to take up a new post hear his family home in the East Midlands. Prior to his current job he was boss at Abertawe Bro Morgannwg Health Board.
The process is now on to find his replacement. There are many difficult issues the new boss will have to handle - how to cope with the current system, plan for the future and keep everyone happy.