The name is a corruption of Owhariu, where, according to Māori mythology, Kupe dried the sails of his canoe.

[2] The name of the locality has given its name to two general electorates: Ōhāriu (first formed for the 1978 election without macrons) and Ohariu-Belmont (which existed from 1996 to 2008).

[6] In the 19th century, Ohariu was divided into Country Sections by the New Zealand Company.

[7] From 1916 there was a dairying invasion which lasted fifty years, because of a better return than from sheep.

Before the 2023 census, the statistical area had a larger boundary, covering 177.49 km2 (68.53 sq mi).