Mayor Jono Naylor's letter of resignation was received by Palmerston North City Council's chief executive Paddy Clifford today.
Following that, Electoral Officer Dr John Annabell announced a by-election. Nominations will open on Monday, 24 November and close at 12noon Monday, 22 December.
If the number of nominations exceeds the vacancy then an election will be held on 10 February 2015. The timing of the election is set under the Local Electoral Act 2001.
Jono Naylor held the mayoralty for seven years and was first elected to Palmerston North City Council as a Councillor in 2001.
Mr Clifford says Deputy Mayor Jim Jefferies will undertake mayoral duties until the new mayor is elected.
Dr Annabell says the by-election will use the Single Transferable Voting (STV) electoral system and will be conducted by postal voting.
Residents and ratepayers of Palmerston North who are not listed on the final electoral roll for the elections can enrol at Post Shops, Libraries or at the Palmerston North City Council Customer Service Centre before 10 February 2015. Such persons will also need to apply for a special vote.
Special Voting facilities will be available at Council's Customer Service Centre, 32 The Square, during normal office hours between 20 January and 10 February 2015.