Diamond Harbour is a small town on Banks Peninsula, in Canterbury, New Zealand. It is on the peninsula's northern coast, on the southern shores of Lyttelton Harbour, and is administratively part of the city of Christchurch.

Banks Peninsula is a peninsula of volcanic origin on the east coast of the South Island of New Zealand. It has an area of approximately 1,150 square kilometres (440 sq mi) and encompasses two large harbours and many smaller bays and coves. The South Island's largest city, Christchurch, is immediately north of the peninsula.