The galah (/ɡəˈlɑː/; Eolophus roseicapilla), less commonly known as the pink and grey cockatoo or rose-breasted cockatoo, is an Australian species of cockatoo and the only member of the genus Eolophus. The galah is adapted to a wide variety of modified and unmodified habitats and is one of Australia's most abundant and widespread bird species. The species is endemic to mainland Australia. It was introduced to Tasmania, where it is now widespread, in the mid-19th century and much more recently to New Zealand.

The term galah is derived from gilaa, a word from the Yuwaalaraay and neighbouring Aboriginal languages spoken in north-western New South Wales.

The galah is about 35 cm (14 in) in length, and weighs 270–350 g (10–12 oz). It has a pale silver to grey back, a pale grey rump, a pink face and breast, and a light pink mobile crest. It has a bone-coloured beak, and the bare skin of the eye ring is carunculated. It has grey legs. The sexes appear similar; however, adult birds differ in the colour of the irises; the male has very dark brown (almost black) irises and the female has mid-brown or red irises. Adults are more brightly coloured than juveniles. Juveniles have a greyish breast, crown, and crest, and brown irises with whitish non-carunculated eye rings.

The galah can be found throughout Australia, and is absent only from the driest areas and the far north of Cape York Peninsula. The galah has been introduced to Tasmania through anthropogenic means and there were no sightings prior to 1848. A large population expansion occurred in the 1960s following many escapees from captivity. It is common in metropolitan areas such as Adelaide, Perth, and Melbourne, and abundant in open habitats that offer at least some scattered trees for shelter. It is common in all habitats in its range except for dense forests, especially those with high rainfall.

While it is mostly found in inland areas, the galah is rapidly colonising coastal regions. The changes brought by European settlement, which have been disastrous for many species, have been highly beneficial for the galah, because of the clearing of forests in fertile areas and the provision of stock-watering points in arid zones.

The galah was also introduced to New Zealand in the latter part of the 20th century, becoming established in the South Auckland area.

The classification of the galah was difficult. It was separated in the monotypic genus Eolophus, but the further relationships were not clear. Obvious morphological similarities are shared between the galah and the white cockatoos that make up the genus Cacatua and indeed the galah was initially described as Cacatua roseicapilla. Early DNA studies allied the galah with the cockatiel or placed it close to some Cacatua species of completely different appearance. In consequence, the ancestors of the galah, the cockatiel and Major Mitchell's cockatoo were thought to have diverged from the main white cockatoo line at some stage prior to that group's main radiation; this was indeed correct except for the placement of the cockatiel. Ignorance of this fact, however, led to attempts to resolve the evolutionary history and prehistoric biogeography of the cockatoos, which ultimately proved fruitless because they were based on invalid assumptions^{[example needed]} to start with.^{[citation needed]}

It fell to the study of Brown & Toft (1999) to compare the previously available data with their mitochondrial 12S rRNA sequence to resolve the issue. Today, the galah is seen, along with Major Mitchell's cockatoo, as an early divergence from the white cockatoo lineage, which has not completely lost its ability to produce an overall pink (Major Mitchell's) or pink and grey (galah) body plumage, while already being light in colour and non-sexually dimorphic. The significance of these two (and other) characteristics shared by the Cacatuinae had previously been explained away in earlier studies by strict application of parsimony on misinterpreted data.