Mr O'Brien says he believes now "is the right time for this change"
The Director General of the HSE has announced his intention to retire from the role this summer.
Tony O'Brien has held the position for the past six years, and today confirmed he will not continue in the role after his current contract expires in the summer.
The HSE chief is said to have formally informed Health Minister Simon Harris of the decision last week, after making the decision last year.
In a video address to staff, Mr O'Brien said: "In that six years, which been some of the most difficult years for the Irish health service - particularly the earlier years - we have achieved so much together.
"I believe that for me and for the HSE renewal is important. For a whole variety of reasons, not least the new policy context that we've secured, I believe that now is the right time for this change."
In a longer address, he argued that the "health service is the wrong shape and the wrong size" to meet the needs of the Irish population, saying that issues such as overcrowding remain an issue despite improvements in other areas.
However, he also welcomed recently announced plans to improve the current health service, such as the Sláintercare proposals which aim to significantly reform the system.
He also praised the response of health workers during the severe weather last week, saying: "I have never been prouder to work in the HSE with you than I am today, and I want to thank everyone, and I want to thank everyone for the enormous efforts that have gone in in recent days."
Mr O'Brien says his remaining months in the role will allow a recruitment process for his replacement to take place, as well as allowing for a "seamless transition".