Lake Maraetai is one of several artificial lakes formed as part of a hydroelectricity scheme on the Waikato River in the North Island of New Zealand. It is located southeast of Hamilton, close to the town of Mangakino.
It is a relatively small lake, covering only , but it is deep at some points, and the powerhouses (Maraetai I and Maraetai II) at its northern end generate of power.