The flathead galaxias (Galaxias rostratus) is a freshwater fish found in lowland rivers and streams and associated billabongs, backwaters, etc. of the southern Murray-Darling river system in Australia. Flathead galaxias continue a pattern found in Murray-Darling native fish of speciation into upland and lowland habitats. Flathead galaxias are found in lowland habitats, while the mountain galaxias species complex, containing at least seven species of Galaxias (research is ongoing) are found in upland habitats, as well as "midland" or upland/lowland transitional habitats.