The Rangitata Diversion Race or RDR is a combined irrigation and power generation scheme that diverts water from the Rangitata River to irrigate over 66,000 hectares of farmland in Mid-Canterbury, New Zealand. The RDR project was the first major river diversion in New Zealand, and the largest irrigation scheme in the country. It was originally constructed by the Public Works Department between 1937 and 1944. The main canal is 67 km long, 10 m wide and 3 m deep.

The Rangitata River is one of the braided rivers that helped form the Canterbury Plains in southern New Zealand. It flows southeast for 120 kilometres (75 mi) from the Southern Alps, entering the Pacific Ocean 30 kilometres (19 mi) northeast of Timaru. The river has a catchment area of 1,773 square kilometres (685 sq mi), and a mean annual flow of 95 cubic metres per second (3,400 cu ft/s) at Klondyke.