Mercury Bay is a large V-shaped bay on the eastern coast of the Coromandel Peninsula on the North Island of New Zealand. This bay was named by the English navigator Captain James Cook during his exploratory expeditions. By the Māori it was named Te-Whanganui-o-Hei, the great bay of Hei.
On 9 November 1769, Cook landed on the shores of this bay to observe a Transit of Mercury. In 1919, an area of land around Shakespeare Cliff was set aside, and a small memorial was constructed, based on the erroneous notion that it was the location of Cook's observations. But the actual site of Cook's landing and observation was the eastern end of Cook's Beach, near the Purangi estuary. A smaller memorial plinth was established there also.
The mouth of Mercury Bay is ten kilometers across, and its coastline extends some 20 km. On the shore of this bay is the resort town of Whitianga, and a natural harbor is formed by an arm of the bay which extends inland a further six kilometers southward. Several small islets are located at the southern and northern extremities of the bay, and the Mercury Islands are 10 km to the north.
Named locations along Mercury Bay include Buffalo Beach, Wharekaho, Ferry Landing, Shakespeare Cliff, Lonely Bay, Flaxmill Bay, Cooks Beach, Purangi Estuary, Cathedral Cove, Hahei, and Hot Water Beach.
Mercury Bay is a good location for game fishing, with fish such as the marlin living there. This is partly due to the nearby presence of the Te Whanganui-A-Hei (Cathedral Cove) marine reserve: fish may not be caught there, but the plentiful fish in this marine reserve leads to fish straying outside the reserve and good catches outside of it.
- Bailey, Susan; McLintock, A. H. (1966). "Te Ara Encyclopedia of New Zealand". An Encyclopaedia of New Zealand. Ministry for Culture and Heritage / Te Manatū Taonga. Retrieved 2010-04-20.
- Wayne Orchiston 1994, James Cook and the 1769 Transit of Mercury, Carter Observatory ISSN 1173-7263 http://www.transitofvenus.co.nz/docs/CarterObservatoryInfo3.doc