HMNZS Otago (F111) was a Rothesay-class Type 12 frigate, or separately designated, Otago-class frigate acquired from the Royal Navy by the Royal New Zealand Navy (RNZN) before completion. Otago and Taranaki differ from the Royal Navy Rothesays as they were never reconstructed to the Leander standard, with hangar and landing pad for a Wasp a/s helicopter as the main weapon system with a/s torpedoes, depth charges and AS-12 missiles to engage FAC and surfaced submarines. The RNZN frigates were constructed with the long range Type 177 sonar to combine with the only operational MK 20 heavyweight torpedo,(where the RN versions in most cases had an accurate short range Type 174, initially) and provided more comfort for the crew in cafeteria messing and bunk bedding. Otago was launched on 11 December 1958 by Princess Margaret, and was commissioned into the Royal New Zealand Navy on 22 June 1960.
Otago took part in various Southeast Asia Treaty Organization (SEATO) deployments and took part in a protest against French nuclear tests at Mururoa Atoll in 1973.
In the weeks preceding the bomb test, HMNZS Otago was constantly monitored and tested by French Navy Lockheed 2PV-5 Neptune maritime patrol aircraft. The instructions were that Otago project authority, but not engage, if seriously challenged by French frigates, RNZN frigates should do everything to increase distance and not use weaponry. The Neptunes flew various patterns fully testing the Otago’s radar, electronic warfare and IFF passive and active capabilities. HMNZS Otago was flying 3 RNZN battle ensigns, officially as an aid to recognition and to signal this was a RNZN operational warship on a political not a protest mission. The objective was to lead a NZ government and world protest against ‘illegal’ atmospheric testing, demonstrate ability for ‘innocent passage’ in international waters, outside the French territorial 12-mile zone and, while avoiding confrontation, maintain the right to self-defence.
Otago became the RNZN training ship in 1981, and paid off into inactive reserve in November 1983. The vessel was sold for scrap in 1987 and broken up in Auckland.