The stygian owl is 38 to 46cm (15 to 18in) long and weighs about 400 to 675g (14 to 24oz). They have very dark plumage, a blackish face with a pale border and a whitish forehead. The head has long dark feathers that project upward as “ears”. The dark upperparts have buff streaks and bars; the underparts are a dingy buff with dark brown or blackish barring and streaks. The eye is shades of yellow, the bill blue-black to blackish and the feet dark greyish or brownish pink.
The stygian owl inhabits a wide variety of landscapes from sea level to 3,000m (9,800ft) of elevation. Most habitats are fairly open rather than densely forested or purely grassland. They include montane pine, pine-oak and cloud forests, thorn scrub, cerrado, pine plantations and even urban parks.