- OAMARU
- OCEAN CURRENTS AROUND NEW ZEALAND
- OHAKUNE
- OHAU, LAKE
- OLIVER, Walter Reginald Brook
- OLYMPIC GAMES
- OMAPERE, LAKE
- OMBUDSMAN
- ONSLOW, Sir William Hillier, Bt., Fourth Earl, P.C., G.C.M.G.
- OPO
- OPOTIKI
- ORAKAU, SIEGE OF
- ORCHIDS
- ORDER OF ST. JOHN – PRIORY IN NEW ZEALAND
- ORETI RIVER
- ORMOND, Hon. John Davies
- O'RORKE, Sir George Maurice, LL.D., M.A., M.L.C.
- OSTRICH FOOT
- OTAGO MOUNTAINS
- OTAGO PENINSULA
- OTAGO PROVINCE OR PROVINCIAL DISTRICT
- OTAGO REGION
- OTAKI
- OTAKOU – OTAGO
- OTOROHANGA
- OYSTER BORER
- OYSTERCATCHER
- OYSTER, AUCKLAND ROCK
- OYSTER, GOLDEN
- OYSTER, STEWART ISLAND
