Ōtāhuhu is a suburb of Auckland, New Zealand – 13 kilometres (8.1 mi) to the southeast of the CBD, on a narrow isthmus between an arm of the Manukau Harbour to the west and the Tāmaki River estuary to the east. The Auckland isthmus is the narrowest connection between the North Auckland Peninsula and the rest of the North Island, being only some 1,200 metres (3,900 ft) wide at its narrowest point, between the Ōtāhuhu Creek and the Māngere Inlet. As the southernmost suburb of the former Auckland City, it is considered part of South Auckland.

The Manukau Harbour is the second largest natural harbour in New Zealand by area. It is located to the southwest of the Auckland isthmus, and opens out into the Tasman Sea.