New Zealand prime minister Jacinda Ardern has given birth to a baby girl.

Ms Ardern posted a photo on her Instagram account showing her and partner Clarke Gayford with the baby at Auckland City Hospital.

She wrote that she was feeling very lucky to have a given birth to a healthy girl, and that their daughter arrived at 4.45pm weighing 7.3lb.

She thanked everyone for their kindness and said they were all doing well, and also thanked the team at the hospital.