The State Pathologist, Professor Marie Cassidy, is to retire later this year.
In a statement, the Department of Justice said that Prof Cassidy was leaving the position "after a long and dedicated service in the office".
The department said that while she will be officially retiring on 31 December, she will effectively be finishing in September.
It said she would still be available to provide expert opinion at relevant inquest and court proceedings for her recent cases.
The department added that the Public Appointments Service (PAS) is running a competition to fill the upcoming vacancy arising from her retirement.
Prof Cassidy joined the Office of the State Pathologist in January 1998 and succeeded Dr John Harbison as State Pathologist in January 2004.
Minister for Justice and Equality, Charlie Flanagan, thanked Prof Cassidy "for her many years of dedicated service".
He said: "The Office of the State Pathologist is a vital part of the criminal justice system.
"The expertise of its forensic pathologists has helped resolve many crimes and bring perpetrators to justice and in doing this work it has been expertly led by Prof Cassidy."
The office is headed by the State Pathologist, who is assisted by two deputies, Dr Micheal Curtis and Dr Linda Mulligan, and a part-time assistant pathologist, Dr Margo Bolster.
A new acting deputy pathologist will also be joining the office later this month.
