thumb|left|Kaiapoi River through [[Kaiapoi, with the Courtenay Stream on the top right]]The Kaiapoi River is a minor river of north Canterbury, in New Zealand's South Island. Originally called the Cam River, it is a tributary of the Waimakariri River, which it joins at the larger river's estuary. The river is long, and its drainage area is about .
The towns of Rangiora, Kaiapoi and Woodend are situated on the banks of the river. This was thought to be due to a change in the profile of the riverbed after the 2011 Christchurch earthquake allowing seawater to progress further upstream.