The ghost bat (Macroderma gigas) is a species of bat found in northern Australia. It is the only Australian bat that preys on large vertebrates – birds, reptiles and other mammals – which they detect using acute sight and hearing, combined with echolocation, while waiting in ambush at a perch. The wing membrane and bare skin is pale in colour, their fur is light or dark grey over the back and paler at the front. The species has a prominent and simple nose-leaf, with large elongated ears that are joined at the lower half, sharp teeth for attacking prey and large dark eyes. The first description of the species was published in 1880, since when its recorded range has significantly contracted.

A species of Macroderma, one of several genera in the family Megadermatidae (false vampires). The family all have large eyes, a nose-leaf and tragus, long ears joined at the base, and are also found in southern Asia and central Africa. The description was published in 1880 by George Dobson, emerging from an examination of specimens held by the Göttingen Museum. The author compared his specimen to taxa named as species of Megaderma, identifying species Megaderma spasma (lesser false vampire bat) as the closest in resemblance. A revision of bat genera by Gerrit Smith Miller Jr. reassigned the species to a new genus Macroderma, creating the current generic combination. The name Macroderma gigas combines the Greek words macros (large) and derma (skin), due to the large size of their partially conjoined ears (Richards, 2012). The epithet gigas (giant) denotes it as the largest species in the family (Hudson, 1986). The species M. gigas is placed with the Megadermatidae. An arrangement separating a "Pilbara district" population as subspecies Macroderma gigas saturata is noted as synonymous with this species concept (MSW 3rd ed., 2005).

The specimen had previously been described by Gerard Krefft in a communication to the Zoological Society of London, and had been forwarded to the Göttingen museum by Dr. Schuette. The description and illustration were presented to the society in 1879, accompanied by the suggestion that it was an unnamed genus of Phyllostomatidae (New World leaf-nosed bats); a member of the society, Edward Richard Alston, proposed instead it was a species of Megaderma which were unknown in Australia. The type locality is at the Wilson River near Mt Margaret in Queensland, where the collector, also named Wilson, obtained the bat. An earlier observation had been noted by Robert Austin in 1854 at Mount Kenneth while surveying the inland regions of Western Australia.

Studies of brain structures indicate that Macroderma gigas is an intermediate and divergent species of the insectivorous microchiropterans and the carnivorous species from South America.

Common names that refer to Macroderma gigas have included ghost bat, false vampire, false vampire bat, and Australian false vampire bat. The name ghost bat derives from its distinct colouring, the predominant colour of its fur may be near white or pale grey.

A larger species of microchiropterans (microbats) and the largest in Australia, the size is comparable to the megabat species (flying fox, fruitbat). The fur colour is grey, ranging in tone from mid, sometimes dark, to very pale grey at the back and whitish at the ventral side and head. The colour of populations is a geographic cline, becoming darker toward the coastal regions. A ring at the eye is dark and colour of the wing membranes and other bare skin is pale and brownish. The interfemoral membrane extends the wing surface between the length of the legs. The great length of the ear, from notch at head to tip, is 44 to 56 millimetres and they are fluted in form; the inner margins of the ears are fused for half their length. The length of the prominent ears is twice that of the head, a seam at the inner margins stiffens these to keep them upright while in flight.

Other measurements of the species are a 96 to 112 mm (3.8 to 4.4 in) range for the forearm length, 98 to 120 mm (3.9 to 4.7 in) for the combined length of the head and body, and a weight range of 75 to 145 g (2.6 to 5.1 oz).

The eyes are comparatively large and well developed for nocturnal vision, a feature shared with the long-eared genera Nyctophilus. The nose-leaf is also large and prominent, and simple in form. The nasal appendage is presumably similar in usage to the elaborate forms of the horse-shoe and leaf-nosed bat genera, manipulating, directing and receiving echolocation signals to detect prey. The lack of a tail, effectively absent, is a characteristic of the species. The membrane at the rear is, however, supported by a calcar at the ankle. The teeth and short robust jaw allow the consumption of a wide variety of animals, either the flesh and bones of other vertebrate species or hard shells of larger invertebrates. Ghost bats are known for their unique hunting behavior, which includes ambushing prey from perches and using their powerful jaws to capture and consume various vertebrates, including small mammals, birds, reptiles, and amphibians. A pregnant bat possesses two sets of teats, one pair beneath the armpits provide milk from the mammary glands and another pair at the pubic area. The pubic teats do not have a lactational function, rather they act as purchase points for the new-born to be carried in flight by the mother.