Octavius Hadfield (born 6 October 1814 at Bonchurch, Isle of Wight, United Kingdom - died 11 December 1904 at Edale, near Marton, Manawatu, New Zealand) was Archdeacon of Kapiti, Bishop of Wellington from 1870 to 1893 and Primate of New Zealand from 1890 to 1893. A missionary for thirty years, he was recognised as an authority on Maori customs and language. His views on Maori rights, expressed in several books strongly criticised the actions of the New Zealand Government.
Following the Wairau Affray in 1843, where a confrontation between Te Rauparaha and group of settlers left twenty-two Europeans dead, many settlers believed an attack on then thinly populated Wellington was possible and Hadfield was seen as a peacemaker preventing the spread of hostilities. Hadfield became far less popular when in 1860, Hadfield upheld Wiremu Kingi's claim to the Waitara block. The surveying of this land prior to military occupation precipitated the First Taranaki War, and Hadfield became a leading critic of the Government in these actions. He "was for some time the most unpopular man in the colony".