An artist's impression of the HMNZS Aotearoa.

The Navy has announced its largest-ever ship - a 24,000-tonne vessel which will cost nearly half a billion dollars - will be called Aotearoa.

Construction of the ship will start next year, for delivery in January 2020.

The 173-metre long vessel will be built by Hyundai Heavy Industries at a projected cost of $493 million.

It would replace the navy's current fuel replenishment ship Endeavour, but carry out a greater number of roles.

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"Aotearoa will have the ability to deploy anywhere in the world to support maritime operations and enhance our combat force," Chief of Navy Rear Admiral John Martin said.

NAVY The HMNZS Aotearoa, compared with some of the navy's existing ships.

"It has the ability to conduct embarked helicopter operations and will be capable of carrying a significant tonnage of operational supplies. And it will provide an important Antarctic support capability to assist with our Southern Ocean monitoring."

Aotearoa would "represent us as a nation on the international stage whether conducting operational support, maritime sustainment or providing humanitarian aid and disaster relief. Aotearoa will be recognisable within the Pacific region and identifiable with all New Zealanders," Martin said.