Taumarunui is a town in the King Country of the central North Island of New Zealand. It is on an alluvial plain set within rugged terrain on the upper reaches of the Whanganui River, 65 km south of Te Kūiti and 55 km west of Tūrangi. It is under the jurisdiction of Ruapehu District and Manawatū-Whanganui region.

It has a population of 4,940 as of June 2025, and is the largest centre for a considerable distance in any direction. It is on State Highway 4 and the North Island Main Trunk railway.

The name Taumarunui is reported to be the dying words of the Māori chief Te Peehi Turoa – taumaru meaning screen and nui big, literally translated as Big Screen, being built to shelter him from the sun, or more commonly known to mean – "The place of big shelter". There are also references to Taumarunui being known as a large sheltered location for growing kūmara.

In the 1980s publication Roll Back the Years there are some details on how Taumarunui got its name. Extract: "According to Frank T Brown, who wrote in the Taumarunui Press in 1926, the name Taumarunui is closely connected with the arrival of and conquering of that portion of the King Country by the Whanganui River natives during the 18th century . . . The war party that succeeded in capturing the principal pa and taking prisoner the chief of the district was headed by 'Ki Maru'. His warriors, to show their appreciation of his prowess and the honour of the victory, acclaimed him 'Tau-maru-nui', which means 'Maru the Great', or 'Maru the Conqueror', that name was taken for the district and has been used ever since."

On State Highway 4 south of Taumarunui are the villages of Manunui, Piriaka, Kakahi, Ōwhango, Raurimu and then National Park. To the north are the school and truck stop of Māpiu.

Taumarunui was originally a Māori settlement at the confluence of the Ongarue River with the Whanganui, important canoe routes linking the interior of the island with the lower Whanganui River settlements. Some places, notably the valley of the Pungapunga Stream, which joins the upper Whanganui near Manunui, were celebrated for the size and quality of tōtara, and large canoes were built there. The area is a border area between a number of iwi including Whanganui, Ngāti Maniapoto and Ngāti Tūwharetoa, who lived together in relative harmony.

Late in December 1843 Bishop Selwyn travelled from the district south of Taupō to a point on the Whanganui River about six miles downstream from Taumarunui and thence continued his journey to the coast by canoe. Towards the end of 1869 Te Kooti was at Taumarunui before his march through the western Taupō district to Tapapa. In the early 1880s the first surveys of the King Country commenced, and by the early 1890s the Crown had begun the purchase of large areas of land.

In 1874, Alexander Bell set up a trading post, and became the first European settler. The town has a road called Bell Road.