The eastern whip-poor-will is a medium-sized bird within the nightjar family, Caprimulgidae, from North America. The whip-poor-will is commonly heard within its range, but less often seen because of its camouflage. It is named onomatopoeically after its song.

Nightjars are medium-sized nocturnal or crepuscular birds in the family Caprimulgidae and order Caprimulgiformes, characterised by long wings, short legs, and very short bills. They are sometimes called goatsuckers, due to the ancient folk tale that they sucked the milk from goats, or bugeaters, their primary source of food being insects. Some New World species are called nighthawks. The English word "nightjar" originally referred to the European nightjar.