Veteran Labour MP Annette King won't be standing for Rongotai in the next general election.
Ms King, 69, has held the electorate in southern Wellington for the past 20 years. Before that she held Miramar and Horowhenua.
Ms King told Newshub on Saturday she has "thought long and hard" about stepping aside, but believes it is the right time.
"It's with a heavy heart that I do it because I love this electorate, but the time is right for a new person to step up and take over," she said.
She will remain on Labour's list.
Ms King denied she's leaving Rongotai so Labour leader Andrew Little can stand there, despite him living in the area and currently only being in Parliament thanks to his position on the list.
Mr Little has twice failed to win the New Plymouth seat, and only narrowly made it into Parliament in the 2014 election.