Waiaua or Lower Waiaua is a rural community in the Ōpōtiki District and Bay of Plenty Region of New Zealand's North Island, located around the lower part of the Waiaua River. The area is in the traditional tribal area of Whakatōhea. The New Zealand Ministry for Culture and Heritage gives a translation of "waters containing herring" for Waiaua. Aua is usually translated as yellow-eye mullet.