The Madagascar hissing cockroach (Gromphadorhina portentosa), also known as the hissing cockroach or simply hisser, is one of the largest species of cockroach, reaching 5 to 7.5 centimetres (2 to 3 inches) at maturity. They are native to the island of Madagascar, which is off the African mainland, where they are commonly found in rotting logs. It is one of some 20 known species of large hissing roaches from Madagascar, many of which are kept as pets, and often confused with one another by pet dealers; in particular, G. portentosa is commonly confused with G. oblongonota and G. picea.

Unlike most cockroaches, they are wingless; The “hissing” sound (expelling air through their bodies) is their primary defense, to frighten potential predators, as they cannot fly and are easily captured. They can reproduce asexually, but usually reproduce sexually. They are excellent climbers and can scale smooth glass. Males can be distinguished from females by their thicker, hairier antennae and the very pronounced "horns" on the pronotum. Females carry the ootheca internally, and release the young nymphs only after her offspring have emerged within her. As in some other wood-inhabiting roaches, the parents and offspring will commonly remain in close physical contact for extended periods of time. In captivity, these insects have been known to live up to 5 years. They feed primarily on vegetable material.