Owlet-nightjars are small nocturnal birds related to the nightjars and frogmouths. Most are native to New Guinea, but some species extend to Australia, the Moluccas, and New Caledonia. A large, flightless species known as Megaegotheles novaesealandiae became extinct as a consequence of human coloniation of New Zealand.

They were thought to have originated in Australasia or Southeast Asia, but the recent discovery of owlet-nightjar fossils in France dating back to the Oligocene suggests otherwise.

The relationship between the owlet-nightjars and other groups within the Caprimulgiformes has long been controversial and obscure and remains so today: in the 19th century they were regarded as a subfamily of the frogmouths, and they are still generally considered to be related to the frogmouths and/or the nightjars but there have also been recent suggestions that they are not so closely related to either as previously thought, and may merit subordinal status.

In form and habits, however, they are very similar to both groups— or, at first glance, to very small owls with huge eyes. Owlet-nightjars are nocturnal insectivores which hunt mostly in the air but sometimes on the ground; their soft plumage is a crypic mixture of browns and paler shades, they have fairly small, weak feet (but larger and stronger than those of a frogmouth or a nightjar), a tiny bill that opens extraordinarily wide, surrounded by prominent whiskers. The wings are short, with 10 primaries and about 11 secondaries; the tail long and rounded.

• ORDER CAPRIMULGIFORMES
• Family Steatornithidae: Oilbird
• Family Podargidae: frogmouths, 13 species in 2 genera)
• Family Aegothelidae
  • Feline Owlet-nightjar , Aegotheles insignis
  • Australian Owlet-nightjar, Aegotheles cristatus
  • New Caledonian Owlet-nightjar , Aegotheles savesi
  • Barred Owlet-nightjar , Aegotheles bennettii
  • Wallace's Owlet-nightjar , Aegotheles wallacii
  • Archbold's Owlet-nightjar , Aegotheles archboldi
  • Mountain Owlet-nightjar , Aegotheles albertisi
  • Spangled Owlet-nightjar , Aegotheles tatei
  • Moluccan or Long-whiskered Owlet-nightjar , Aegotheles crinifrons
• Family Nyctibiidae: potoos, about 6 species in 2 genera)
• Family Caprimulgidae: nightjars, about 70 or 80 species in about 15 genera)