John Larkin QC has served as the Stormont Executive’s chief legal adviser for 10 years.
His current term of office ends at the end of June, and he has decided not to seek another.
Mr Larkin was appointed a temporary High Court judge earlier this year.
First Minister Arlene Foster and deputy First Minister Michelle O’Neill thanked Mr Larkin in a joint statement.
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“On behalf of the Executive, we would like to thank Mr Larkin for his tireless and invaluable work over the past decade,” they said.
“The Executive Office will initiate a selection process to help identify and appoint Mr Larkin’s successor.
“This process will be based on the principles that apply to public appointments and will be an open competition.”
The ministers said a number of options for interim arrangements to fill the position of the Attorney General were being considered.