The dark-billed cuckoo (Coccyzus melacoryphus) is a species of bird in the tribe Phaenicophaeini, subfamily Cuculinae of the cuckoo family Cuculidae. It is regularly found in every mainland South American country except Chile plus the Galápagos Islands. It has also occurred as a vagrant in Chile and several other countries and islands.
Adults have a gray crown and nape and grayish brown upperparts. Their wings are a darker grayish brown with no rufous. The upper surface of their tail is brown; the underside of the central pair of feathers is brown with black tips, the next pair blackish with narrow white tips, and the rest black with wide white tips. Their face is gray with a wide black "mask" past the eye, which is surrounded by a narrow ring of citron yellow, olive yellow, or gray bare skin. Their underparts are pale buff with the breast somewhat darker than the rest; the sides of the breast and flanks are gray. Juveniles are similar to adults but duller, with a brown crown and nape, gray tips on the tail feathers, and sometimes rufous in the wings.