Kaiapoi is a town in the Waimakariri District of the Canterbury region, in the South Island of New Zealand. The town is located approximately 17 kilometres north of central Christchurch, close to the mouth of the Waimakariri River. It is considered a satellite town of Christchurch and is part of the Christchurch functional urban area.

Kaiapoi is known for its substantial precolonial pā, established by powerful Kāi Tahu nobleman Tūrākautahi. One of the sons of the powerful rangatira Tūāhuriri, Tūrākautahi exerted vast influence over historical Ōtautahi (the site of modern-day Christchurch). His family controlled the pā he established in the area until it was sacked in 1830. The pā was one of the greatest centre of knowledge, economics and natural resources, with a highly complex social structure. All decisions were undertaken by the nobility, who consulted with highly skilled tohunga. In selecting the pā site, Tūrākautahi determined that food (kai) would need to be poi (“swung in”- swung over the pā’s protective walls via rope, and also because it lay in the middle of a swamp) from other places.This is how Kaiapoi got its name, and can translated as a metaphor for “economics”.

It had an estimated population of 13,400 as of June 2022.

Kaiapoi is also known as the ‘River Town’ after the Kaiapoi River, a tributary of the Waimakariri River that flows through the centre of the town. This was originally the main arm of the Waimakariri River, but extensive flooding led to a diversion so the majority of the water travelled down the South arm of the Waimakariri.