The powerful owl (Ninox strenua), a species of owl native to south-eastern and eastern Australia, is the largest owl on the continent. It is found in coastal areas and in the Great Dividing Range, rarely more than 200 km (120 mi) inland. The IUCNRed List of Threatened Species also refers to this species as the powerful boobook. An apex predator in its narrow distribution, powerful owls are often opportunists, like most predators, but generally are dedicated to hunting arboreal mammals, in particular small to medium-sized marsupials. Such prey can comprise about three-quarters of their diet. Generally, this species lives in primary forests with tall, native trees, but can show some habitat flexibility when not nesting. The powerful owl is a typically territorial raptorial bird that maintains a large home range and has long intervals between egg-laying and hatching of clutches. Also, like many types of raptorial birds, they must survive a long stretch to independence in young owls after fledging. Unlike most raptorial birds, however, male powerful owls are larger and stronger than females, so the male takes the dominant position in the mating pair, which extends to food distribution.
The powerful owl has a long tail and a small head, giving it an atypical silhouette for an owl and imparting a more hawk-like appearance than any other large owl. The protruding bill and distinct brow ridges enhance the hawk-like appearance of the species. The facial disc is ill-defined. The upper parts are dark grey-brown, mottled, and barred with whitish. The underparts are white with bold, grey-brown, V-shaped barring. The tail has six narrow white bars contrasting with grey-brown. This species has large yellow eyes, with greyish feathering down to the base of the toes and feet of a dull yellow color. They are aptly named, with very powerful and heavy claws. This owl is the largest species of the "hawk owl" group found in much of Asia and the Australasian region, all included in the genus Ninox. It can be considered, along with its sister species the rufous owl (N. rufa), as Australia's analogue to the genus Bubo.