The Firth of Thames (Māori: Tikapa Moana-o-Hauraki) is a large bay located in the north of the North Island of New Zealand. It is the firth of the rivers Waihou and Piako, the former of which was formerly named the Thames River, and the town of Thames lies on its southeastern coast. Its Maori name is Tikapa. In traditional legend, the firth and the greater Hauraki Gulf are protected by a taniwha named Ureia, who takes the form of a whale.