The SDLP’s Karen McKevitt will not contest next year’s Assembly election.
The South Down representative, who has been an MLA since 2011, is considering quitting public life completely.
She said: “After much soul-searching I have decided not to seek the party’s nomination for South Down.
“I am currently exploring a number of options which may take me away from the world of politics.”
Ms McKevitt, a former Newry and Mourne District councillor, has long campaigned for defibrillators to be installed in all public buildings across Northern Ireland after her father died from a heart attack aged 47.
“I am proud of the contribution that I and my team have made,” she added.
SDLP leader Alasdair McDonnell described her as a “fierce advocate” for local people.
“We all sincerely hope that Karen remains involved in public life,” he said.