Kokila or the Asian koel (Eudynamys scolopaceus) is a member of the cuckoo order of birds, the Cuculiformes. It is found in the Indian Subcontinent, China, and Southeast Asia. It forms a superspecies with the closely related black-billed and Pacific koels which are sometimes treated as subspecies. The Asian koel is a brood parasite that lays its eggs in the nests of crows and other hosts, who raise its young. They are unusual among the cuckoos in being largely frugivorous as adults. The name koel is echoic in origin with several language variants. The bird is a widely used symbol in Indian poetry.

Kokila is a large, long-tailed, cuckoo measuring 39–46 cm (15–18 in) and weighing 190–327 g (6.7–11.5 oz). The male of the nominate race is glossy bluish-black, with a pale greenish grey bill, the iris is crimson, and it has grey legs and feet. The female of the nominate race is brownish on the crown and has rufous streaks on the head. The back, rump and wing coverts are dark brown with white and buff spots. The underparts are whitish, but is heavily striped. The other subspecies differ in colouration and size. The upper plumage of young birds is more like that of the male and they have a black beak. They are very vocal during the breeding season (March to August in the Indian Subcontinent), with a range of different calls. The familiar song of the male is a repeated koo-Ooo. The female makes a shrill kik-kik-kik... call. Calls vary across populations.

The word "koel" is onomatopoeic in origin. The Sanskrit name of "Kokila" and words in several Indian languages are similarly echoic. Being familiar birds with loud calls, references to them are common in folklore, myth and poetry. It is traditionally held in high regard for its song and revered in the Manusmriti, an ancient decree protecting them from harm. The Vedas, Sanskrit literature dated to about 2000 BC referred to it as Anya-Vapa which has been translated as "that which was raised by others" (or "sown for others to reap"). This has been interpreted as the earliest knowledge of brood parasitism.