Porirua Harbour is a natural inlet in the south-western coast of the North Island of New Zealand. The city of Porirua, one of the four cities in the Wellington conurbation, surrounds it. The city centre is to the south of the harbour. The harbour has an entrance only a few hundred metres in width, close to the suburb of Plimmerton. It opens up into two arms, Porirua Inlet to the south and Pauatahanui Inlet to the north-east.