Te Whanganui-A-Hei (Cathedral Cove) Marine Reserve is on the Coromandel Peninsula in New Zealand covering an area of 840 hectares (2,100 acres). Cathedral Cove is named after the cave located there, linking Mare's Leg Cove to Cathedral Cove. Gemstone Bay and Stingray Bay are also located within the reserve. A walking track exists from the northern end of Hahei Beach, and it is also possible to walk from the local authority car park at the top of the headland between Hahei and Gemstone Bay. The area is very popular with tourists, and receives around 150,000 visitors per year.
Boat and kayaking tours come from Whitianga in the north and Hahei in the south to visit the area. Both coves contain shapely natural rock stacks, Sphinx Rock in Mare's Leg Cove, and Te Hoho Rock in Cathedral Cove. Stingray Bay, and in particular Gemstone Bay, are popular snorkelling and diving areas, as marine life within the reserve boundaries is plentyful. In Gemstone Bay there is also a snorkel trail marked by the Department of Conservation. Both bays are also accessible by paths leading down from the main walking path to Cathedral Cove.
The Māori name Te Whanganui-A-Hei (the Great Bay of Hei) refers to Hei, a tohunga from the Te Arawa waka. According to tradition, Hei chose the area around Mercury Bay as home for his tribe, proclaiming ownership by calling Motueka Island "Te Kuraetanga-o-taku-Ihu" (the outward curve of my nose.) It is said he made this claim near the site of the present-day of Hahei.