Acrothamnus colensoi is a plant species from the family Ericaceae and is endemic to New Zealand. It is a short shrub that can spread to form mounds of up to 2 m across. It can be found in both the North and South Islands, in scrub, tussock grassland and peat bogs, south of the Kaingaroa Forest. A. colensoi was named in honour of William Colenso, a New Zealand missionary, botanist and politician.