The giant coot (Fulica gigantea) is a species of bird in subfamily Rallinae of family Rallidae, the rails, gallinules, and coots. It is found in Argentina, Bolivia, Chile, and Peru.

The giant coot is the second largest extant member of family Rallidae, after the takahē of New Zealand. Adults are 48 to 59 cm (19 to 23 in) long. They weigh about 2,000 to 2,500 g (4.4 to 5.5 lb) and are too heavy to fly, though immature birds are smaller and readily fly. The sexes are alike. Adults have a bulky body and a disproportionately small head. Their plumage is deep slaty gray that is blacker on the head and neck. Their undertail coverts have some white streaking. Their bill is deep red with some yellow at the base of the maxilla, their frontal shield is yellow, and unique among coots their legs and feet are deep red. Immature birds have dark gray underparts and a paler bill and legs than adults. Juveniles are dark dull gray with some white on the face and dusky legs.