Blockhouse Bay is a residential suburb in the south west of Auckland, in New Zealand's North Island. It is sited on the northern coast of the Manukau Harbour, and is also close to the administrative boundary that existed between Auckland City and Waitakere City, two of the former four cities of what was the Auckland conurbation before amalgamation into Auckland Council. The suburb is located 11 kilometres to the southwest of the city centre, and is surrounded by the more central suburbs of Lynfield and New Windsor, and the Waitakere suburbs of New Lynn and Green Bay.