The fishes in this genus have a circumglobal distribution in the deep waters of the tropical and temperate zones of the Atlantic, Indian and Pacific Oceans.

[3] The type locality of G. vanhoeffeni was given as the Indian Ocean east of Zanzibar from Valdivia station 239 from the surface to a depth of 2,500 m (8,200 ft).

[6] The fifth edition of Fishes of the World classifies the whipnose anglers within the suborder Certioidei within the order Lophiiformes, the anglerishes.

[8] Giganactis contains 22 recognized extant species:[9] Gigantactis whipnose anglers are distinguished from the other genus in the family, Rhynchactis, by the absence of pelvic bones and by the possession of between 5 and 9 rays, rarely 4 or 10, in the dorsal fin and the anal fin containing between 5 and 7, rarely 4 or 8, soft rays.

The metamorphosed males have larger eyes than those of Rhynchactis, typically having 12 olfactory lamellae, deep nostrils with a depth greater than 9% of the standard length.