The Black Sicklebill, Epimachus fastuosus is a large bird of paradise of midmountain forests of New Guinea. The male has black plumage with an iridescent green, blue and purple scale-like feathers, red iris, bright yellow mouth, long curved black bill, huge sabre-shaped tail and large erectile fan-like plumes on sides of breast. The female is smaller than the male. It has a reddish brown plumage with brown iris and buff below.

With up to 110cm in length, the male Black Sicklebill is the largest of Paradisaeidae in terms of overall length, though the Curl-crested Manucode has a larger body. The diet consists mainly of fruits and arthropods. The male is polygamous and performs a horizontal courtship display with the pectoral plumes raised around its head.

In the wild, the bird has hybridised with the Arfak Astrapia creating offspring that were once considered a distinct species, the Elliot's Sicklebill, Epimachus ellioti. While some believe this was a valid species that is possibly critically endangered or extinct, it is generally viewed by most mainstream ornithologists as a hybrid.

Due to ongoing habitat loss, small population size and hunted in some areas for food and its tail feathers, the Black Sicklebill is classified as Vulnerable on the IUCN Red List of Threatened Species. It is listed on Appendix II of CITES.