Tropical box jellyfish include some of the world's most venomous animals, leading researchers and the media to wonder whether changes in climate may drive these species into sub-tropical waters. The discovery, therefore, of small box jellyfish in the waterways of the Gold Coast and Sunshine Coast of south-east Queensland raised concern. This pygmy species proved to be new to science, separated from other species in the genus Chiropsella by its very small size; its semi-circular phacellae; very shallow, coalesced gastric saccules; its peculiar, long pedalia where the ‘palm’ is greatly reduced and the non-opposing ‘fingers’ branch off together at the same level; and a knee-like bend of the pedalial canal. The residential canal/river habitat of this species of chirodropid raises the question of whether this area is also suitable for habitation by the larger, more virulent chirodropids such as the so-called ‘deadly box jellyfish’, Chironex fleckeri. This new species, Chiropsella saxoni sp. nov., brings the total number of chirodropid species described from Australian waters to five.