The Giant Ibis, Thaumatibis gigantea, the only species in the monotypic genus Thaumatibis, is a wading bird of the ibis family, Threskiornithidae. It is confined to northern Cambodia, with a few birds surviving in extreme southern Laos.

It occurs in marshes, pools, wide rivers and seasonal water-meadows in deciduous, lowland forest. It eats invertebrates, crustaceans, small amphibians and reptiles. Nothing is known of its breeding behaviour, but it probably nests in trees.

This is, by far, the largest of the world's ibises. Adults are reportedly 102"?106 cm (40"?42 in) long and are estimated to weigh about 4.2 kg (9.3 lbs). The adults have dark plumage with a naked, greyish head and upper neck.

This bird is considered to be critically endangered due to hunting, disturbance and lowland deforestation. The current population is estimated at 100 pairs.