The river rises on the northern slopes of Mount Tongariro, one of the three active volcanoes of the central plateau, close to Lake Rotoaira. It flows to the north-west before turning south-west at Taumarunui. From here it runs through the rough, bush-clad hill country of the King Country before turning south-east and flowing past the small settlements of Pipiriki and Jerusalem, before reaching the coast at Whanganui. It is one of the country's longest navigable rivers.