The Onehunga Ironworks was a colonial-era iron smelting and rolling operation at Onehunga, on the Manukau Harbour, (now a suburb of Auckland, New Zealand). It was at one time claimed to be the largest ironworks in the Southern Hemisphere. It is significant, both as the first large scale attempt to exploit New Zealand's iron-sand by direct reduction, and as a precursor of the modern steel industry of New Zealand.