The Royal New Zealand Navy is the maritime arm of the New Zealand Defence Force. The fleet currently consists of nine ships. The Navy had its origins in the Naval Defence Act 1913, and the subsequent purchase of the cruiser HMS Philomel, which by 1921 had been moored in Auckland as a training ship. A slow buildup occurred during the interwar period, and then perhaps the infant Navy's most notable event occurred when HMS Achilles fought alongside two other Royal Navy cruisers at the Battle of the River Plate against the German ship, Graf Spee, in December 1939.

The New Zealand Defence Force is the three-branched military of New Zealand. The NZDF is responsible for the protection of the national security of New Zealand and her realm, promoting its interests, safeguarding peace and security, as well as supporting peacekeeping and humanitarian missions. It consists of three services: the Royal New Zealand Navy (RNZN), the New Zealand Army and the Royal New Zealand Air Force (RNZAF), as well as 'tri-service' components. As of June 2023, the NZDF has a strength of 14,996 employees, consisting of 8,669 regular force personnel, 3,260 reserve force personnel and 3,067 civilian members. It is supported by the New Zealand Ministry of Defence (MOD) and is commanded by the Chief of Defence Force (CDF).