The Waipaoa River is a river of the northeast of New Zealand's North Island. It rises on the eastern slopes of the Raukumara Range, flowing south for 80 kilometres (50 mi) to reach Poverty Bay and the Pacific Ocean just south of Gisborne. For about half of this distance its valley is followed by State Highway 2. The river has several important tributaries, among them the Wharekōpae, Waikohu, Mangatu, Te Ārai, Waingaromia and Waihora rivers. Major settlements along the banks of the river include Te Karaka, Ormond, and Pātūtahi.

The river has formed the fertile and highly productive Poverty Bay flats on the edge of Gisborne. The Waipaoa River Flood Control Scheme was built in the 1950s. Stopbanks are to be raised by 2031, as soil erosion, especially from the Waingaromia and Mangatu catchments, has built up the river bed, the annual flow of sediment being 15 million tonnes. Despite this pollution, many of the headwaters have indigenous fish. In the lower river, water quality is poor for E. coli, clarity, turbidity, ammoniacal nitrogen and total phosphorus. The sediment, building up at the rate of several centimetres a year, even many kilometres into Poverty Bay, shows that removal of trees such as rimu, matai and kaihikatea and then converting fern covered areas to farmland by the early 20th century, increased sediment flows by 2 to 3 times the former rate.