The Coromandel Peninsula lies in the North Island of New Zealand. It is part of the Waikato region and extends 85 kilometres north from the western end of the Bay of Plenty, forming a natural barrier to protect the Hauraki Gulf and the Firth of Thames in the west from the Pacific Ocean to the east. At its broadest point, it is 40 kilometres wide. Almost the entire population lies on the narrow strips along the Hauraki Gulf and Bay of Plenty coasts. The country's biggest city, Auckland, lies on the far shore of the Hauraki Gulf, 55 kilometres to the west. The peninsula is clearly visible from the city in fine winter weather.
The peninsula is steep and hilly, and is largely covered in subtropical rain forest.
The Coromandel Range forms a spine for the peninsula rising to nearly 900 metres, and the large island of Great Barrier, which lies beyond the northern tip, can be thought of as an extension of the range. Great Barrier is separated from Cape Colville on the peninsula's northern coast by the Colville Channel.
Although the peninsula is close to large centres of population such as Auckland to the west and Tauranga to the southeast, its rugged nature means that much of it is relatively isolated, and the interior and northern tip are both largely undeveloped and sparsely inhabited. A forest park covers much of the peninsula's interior.