Gobiomorphus is a genus of eleotrid gobies, commonly called bullies or gudgeons, native to New Zealand and eastern Australia. The atlas's 7 species range from about 2.5 in to 7 in and are recorded from freshwater and estuarine habitats across both countries — rivers, streams, and lakes, often with a life history tied to the sea, since a number of species are amphidromous, with larvae drifting out to marine or estuarine waters before returning to fresh water as juveniles. They have the typical goby body plan of a blunt head and a robust, elongated body, though unlike true gobies (Gobiidae) their pelvic fins are separate rather than fused into a sucking disc.
Gobiomorphus cotidianus (common bully) is by far the best-known species, widespread throughout New Zealand's lakes and rivers and an important food source for introduced trout, while species such as G. huttoni (redfin bully) and G. hubbsi (bluegill bully) are more habitat-specific, favoring particular stream conditions. The genus is of far more interest to native-fish biologists and New Zealand aquarists than the wider aquarium trade, which rarely sees bullies offered commercially. Conservation status is broadly reassuring — four of the seven atlas species are Least Concern — though one, G. gobioides (giant bully), is assessed Near Threatened, and two remain Not Evaluated.