Rotorua Mayor Tania Tapsell and her husband Kanin Clancy are expecting a baby girl in June.
"As well as delivering for Rotorua as Mayor, three months from now I'll be delivering something very special for my husband and I - a baby girl," Tapsell said.
In a statement on Friday, Tapsell said she feels "blessed" to take on the roles of being both a mayor and a mother.
"We're so excited to be expanding our family and are grateful for the support of my council team," Tapsell said.
"Rotorua has given me so much and I can't wait to raise our baby girl in this great place we call home."
Tapsell was the first Māori woman elected as mayor of Rotorua, and will also be the first known mayor in New Zealand to give birth while holding office.
"I plan to take a short one-month break following the birth and then my supportive husband Kanin will take over from there to allow me to resume my important duties as mayor," Tapsell said.
"Our new council has made great progress for our district already, and I look forward to continuing to build on the positive momentum while enjoying my new role as a mum."
Deputy Mayor Sandra Kai Fong will be acting mayor when Tapsell goes on maternity leave.