The Southern cassowary (Casuarius casuarius) is a large and distinctive flightless bird native to the tropical forests of New Guinea, nearby islands, and northern Australia.

Known for its striking appearance, characterized by vibrant blue and black plumage, a helmet-like casque on its head, and bright blue skin on its neck and face, the Southern cassowary is an iconic and endangered species. With powerful legs and a reputation as one of the world’s heaviest birds, it plays a crucial role in its ecosystem, dispersing seeds and contributing to forest regeneration. Despite its remarkable features, the Southern cassowary faces threats such as habitat loss and road accidents, emphasizing the importance of conservation efforts to protect this unique and vital species.   The southern cassowary has stiff, bristly black plumage, a blue face and a long neck, red on the cape and two red wattles measuring around 17.8 cm (7.0 in) in length hanging down around its throat. A horn-like brown casque, measuring 13 to 16.9 cm (5.1 to 6.7 in) high, sits atop the head. The bill can range from 9.8 to 19 cm (3.9 to 7.5 in). The plumage is sexually monomorphic, but the female is dominant and larger with a longer casque, larger bill and brighter-coloured bare parts. The juveniles have brown longitudinal striped plumage.

The three-toed feet are thick and powerful, equipped with a lethal dagger-like claw up to 12 cm (4.7 in) on the inner toe. It is perhaps the largest member of the cassowary family and is tied as the third heaviest bird on earth (after the Somali ostrich and the common ostrich), at a maximum size estimated at 85 kg (187 lb) and 190 cm (6 ft 3 in) tall. Normally, this species ranges from 127 to 170 cm (4 ft 2 in to 5 ft 7 in) in length. The height is normally 150 to 180 cm (4 ft 11 in to 5 ft 11 in) ; females average 58.5 kg (129 lb), while males average 29 to 34 kg (64–75 lb). The northern cassowary is about the same size on average and is perhaps very mildly less sexually dimorphic than the southern. Most adult birds will weigh between 17 and 70 kg (37 and 154 lb). It is technically the largest Asian bird (since the extinction of the Arabian ostrich) and the largest Australian bird (though the emu may be slightly taller).