It is endemic on the mainland and was introduced to Tasmania,where its distinctive pink and grey plumage and its bold and loud behaviour make it a familiar sight in the bush and increasingly in urban areas. It appears to have benefited from the change in the landscape since European colonisation and may be replacing the Major Mitchell's cockatoo in parts of its range. Galahs are about 35 cm (14 in) long and weigh 270–350 g. They have a pale silver to mid-grey back, a pale grey rump, a pink face and chest, and a light pink mobile crest. They have a bone-coloured beak, and the bare skin of the eye rings is carunculated. They have grey legs. The sexes appear similar, however generally 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. The colours of the juveniles are duller than the adults. Juveniles have greyish chests, crowns, and crests, and they have brown irises and whitish bare eye rings, which are not carunculated.Galahs are found in all Australian states, and are absent only from the driest areas and the far north of Cape York Peninsula. It is still uncertain whether they are native to Tasmania, though they are locally common today, especially in urban areas. They are common in some metropolitan areas, for example Adelaide, Perth and Melbourne, and common to abundant in open habitats which offer at least some scattered trees for shelter. The changes brought by European settlement, a disaster 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.

Flocks of galahs will often congregate and forage on foot for food in open grassy areas.

galahs are known to join flocks of little corellas , and are known to breed with them also.[ A galah/sulphur-crested cockatoo hybrid which was hatched in 1920 was still living in the Adelaide zoo in the late 1970s, being displayed in a small cage alone near the entrance to an on-site cottage. The back feathers were a patchwork of grey tones and the breast feathers a soft apricot tone and the crest a slightly richer orange. The crest was longer that a galah crest but without the long curl of the sulphur-crested cockatoo. The bird was not significantly larger than a galah.[