Onehunga High School is a state co-educational secondary school in the Auckland suburb of Onehunga, New Zealand which provides education for students in Years 9 to 13.

The school attracts students from the suburbs of Onehunga, Māngere Bridge, Hillsborough, and Royal Oak and accepts a limited number of students from outside its zone.

Onehunga High School was "founded" in 1959 by Mr J. C. McCarthy on its Pleasant Street site. At its birth the roll was 190 students but it has grown slowly to a peak of over 1,500. McCarthy was principal from the foundation until his retirement 19 years later.

Onehunga is situated in one of Auckland's suburbs' overlooking the Manukau Harbour. Many Onehunga High School families have long histories in the area and a large number of the students are second- or third- generation students. The school's proximity to Onehunga and Penrose's industrial and retail area has enabled links with some service clubs and businesses, including scholarships and trust funds.

In the early days the school was mono-cultural in character, but during the 1980s it developed towards a multi-cultural school, with increasing numbers of Māori, Polynesian and Asian students. Today the school is strongly international and enjoys all the qualities a wide range of cultures bring.

In the 1980s as part of wider decentralisation changes in the New Zealand education system, the school was provided self-governance under a board of trustees system. In 1996, Onehunga High School opened Te Haerenga, the school marae. From 2000, the school underwent a modernisation and development programme. In 2024 the school created a new learning culture using values in the acronym WAKA.

The school has always received students from Onehunga, Royal Oak, Hillsborough and Māngere Bridge. The main feeder school is Royal Oak Intermediate. With the change of principal in 2022 the roll has increased massively.

As of March 2026, Onehunga High School has a roll of 1,030 students, of which 201 (19.5%) identify as Māori.