The Hauraki Gulf / Tīkapa Moana is a coastal feature of the North Island of New Zealand. It has an area of 4000 km², and lies between, in anticlockwise order, the Auckland Region, the Hauraki Plains, the Coromandel Peninsula, and Great Barrier Island. Most of the gulf is part of the Hauraki Gulf Marine Park.
Hauraki is Māori for north wind. In 2014, the gulf was officially named Hauraki Gulf / Tīkapa Moana
The gulf is part of the Pacific Ocean, which it joins to the north and east. It is largely protected from the Pacific by Great Barrier Island and Little Barrier Island to the north, and by the 80-kilometre-long Coromandel Peninsula to the east. It is thus well protected against all but northern winds.
Three large channels join the gulf to the Pacific. Colville Channel lies between the Coromandel Peninsula and Great Barrier, Cradock Channel lies between the two islands, and Jellicoe Channel lies between Little Barrier and the North Auckland Peninsula. To the north of Auckland several peninsulas jut into the gulf, notably the Whangaparaoa Peninsula. Tiritiri Matangi Island is near the end of this peninsula. Further north, Kawau Island nestles under the Tawharanui Peninsula.
Numerous beaches dot the shores of the gulf, many of them well known for swimming and surfing.
During the last glaciation period the gulf was dry land, with the sea level being around 100–110 m (300 ft) lower than at present. The gulf was submerged when the sea reached its current level around 7200 years ago.
In the west of the gulf lie a string of islands guarding the mouth of the Waitemata Harbour, one of Auckland’s two harbours. These include Ponui Island, Waiheke Island, Tiritiri Matangi and the iconic dome of Rangitoto Island (a dormant volcano), which is connected to the much older Motutapu Island by a causeway. The islands are separated from the mainland by the Tamaki Strait and Rangitoto Channel.
Other islands in the gulf include Browns Island, Motuihe Island, Pakihi Island, Pakatoa Island, Rakino Island, and Rotoroa Island in the inner gulf, around Waiheke and Rangitoto; Tarahiki Island just east of Waiheke; Motukawao Islands and Whanganui Island in the lee of the Coromandel Peninsula; and Channel Island in the outer gulf.