The Wairoa River of the Hawke's Bay region in New Zealand runs south for 65 kilometres from the inland east coast region of the North Island, west of Gisborne, before flowing into northern Hawke Bay at the town of Wairoa.

The full Māori name of the river is Te Wairoa Hōpūpū Hōnengenenge Mātangi Rau, which means the long, bubbling, swirling, uneven waters.^[1]

It has a catchment area of 1,415 square miles (3,660 km²),^[2] which includes Lake Waikaremoana.

The major tributaries are:

• the Hangaroa River
• the Ruakituri River
• the Mangapoike River
• the Mangaaruhe River
• the Waiau River
• the Waikaretaheke River

The Hangaroa River and the Ruakituri River merge at Te Reinga Falls, near Te Reinga. This is where the Wairoa River begins.

Lake Waikaremoana is formed in the rockfall-dammed headwaters of the Waikaretaheke River. It has a confluence with the Waiau River 14 miles from the coast.^[2]

In 1948 a big flood of the Wairoa River submerged the traffic bridge in Wairoa and flooded parts of the town to a depth of 3 feet (0.91 m). This flood flow is one of the largest recorded for any river in New Zealand.^[2] The river rose to a "record height", the bridge "took a battering", and "telephone lines 4.3 metres above road level were carrying grass and twigs, showing the phenomenal rise of the floodwaters".^[3]

In 2010, the Wairoa Township River Walkway project commenced. The Walkway is a pedestrian and cycle path starting at the bridge on the south bank of the Wairoa River. It is planned that it will eventually completely encircle the town.^[4]