Rakaia is a town sited on the southern banks of the Rakaia River on the Canterbury Plains in New Zealand's South Island, approximately 57 km south of Christchurch on State Highway 1 and the Main South Line. Immediately north of the township are New Zealand's longest road bridge and longest rail bridge, both of which cross the wide shingle beds of the braided river at this point. Both bridges are approximately 1,750 metres (5,740 ft) in length.

The Rakaia River is in the Canterbury Plains in New Zealand's South Island. The Rakaia River is one of the largest braided rivers in New Zealand. The Rakaia River has a mean flow of 203 cubic metres per second (7,200 cu ft/s) and a mean annual seven-day low flow of 87 m3/s (3,100 cu ft/s). In the 1850s, European settlers named it the Cholmondeley River, but this name lapsed into disuse. The name Rakaia comes from Māori "Ō Rakaia", meaning the place where people were arranged by ranks.