The Lesser Potoo or Common Potoo (Nyctibius griseus), is a nocturnal bird which breeds in tropical Central and South America from Costa Rica to northern Argentina and northern Uruguay. The Northern Potoo (N. jamaicensis) was formerly classified as a subspecies of this species.

This potoo is a large near passerine bird related to the nightjars and frogmouths, but like other potoos it lacks the bristles around the mouth found in the true nightjars. It is 33-38cm long and pale greyish to brown, finely patterned with black and buff, camouflaged to look like a log; this is a safety measure to help protect it from predators, but its mode of perch is also a camouflage. It has large orange eyes.

The Lesser Potoo can be located at night by the reflection of light from its eyes as it sits on a post, or by its haunting melancholic song, a BO-OU, BO-ou, bo-ou, bo-ou, bo-ou, bo-ou, bo-ou, bo-ou dropping in both pitch and volume.

It is a resident breeder in open woodlands and savannah. It avoids cooler montane regions, rarely occurring over 1,900 meters ASL even in the hottest parts of its range. Also, arid regions are usually avoided; for example in the dry Caribbean plain of Colombia the species was first recorded in April 1999.

This nocturnal insectivore hunts from a perch like a shrike or flycatcher. During the day it perches upright on a tree stump, and is completely invisible, looking like part of the stump because it stays so completely still as it perches.

The single egg is white with lilac spots . It laid directly in a depression in a tree limb, usually some meters above ground. It is not clear whether there can be, on occasion, two eggs in a clutch.