Professor Breda Smyth has been named as Ireland's interim Chief Medical Officer.
She replaces Dr Tony Holohan, who will resign from the position on July 1st.
Health Minister Stephen Donnelly says Prof Smyth will take up the role "pending the completion of the competition to fill the role on a permanent basis".
She is being seconded to the Department of Health on a short-term basis - while an open competition for the permanent position has been advertised.
Prof Smyth has specialised in public health for the last 16 years.
She is currently Professor for Public Health Medicine in NUI Galway and Consultant in Public Health in HSE West.
She also contributed significantly to Ireland's COVID-19 response - having been a member of the National Public Health Emergency Team (NPHET), the Rapid Testing Expert Advisory Group and chief investigator on the multi-site study UniCoV.
Prof Smyth was also a founding member of the COVID-19 Irish Epidemiology Modelling Advisory Group (IEMAG).
Minister Donnelly says: "While the open competition for the permanent filling of the crucial role of Chief Medical Officer has commenced, I am conscious of the need to have in place the required leadership at all times to continue to monitor and combat COVID 19 and other public health threats.
"Prof Smith has a unique skill set with the requisite mix of academic, policy and frontline experience having provided leadership, expert and professional guidance of public health nationally and in HSE West over the last number of years."
On her appointment, Prof Smyth says: "I am excited to have the opportunity to work together with colleagues in the Department of Health, and across our health and social care service to build on the considerable work done, both before and during COVID-19, to promote and protect public health and the health and wellbeing of the population of Ireland.
"The pandemic has placed a spotlight on public health, and I look forward to the opportunity to advance the public health agenda through important, cross-government initiatives".