The Black-crowned Night Heron (in Eurasia, often just Night Heron; in North America, Black-crowned Night-Heron with a second hyphen), (Nycticorax nycticorax) is a medium-sized heron.

Adults are 64 cm long and weigh 800 g. They have a black crown and back with the remainder of the body white or grey, red eyes, and short yellow legs. Young birds are brown, flecked with white and grey. These are short-necked and stout herons.

The breeding habitat is fresh and salt-water wetlands throughout much of the world. The subspecies N. n. hoactli breeds in North and South America from Canada as far south as Patagonia, and the nominate race N. n. nycticorax in Europe, Asia and Africa. Black-crowned Night Herons nest in colonies on platforms of sticks in a group of trees, or on the ground in protected locations such as islands or reedbeds. Three to eight eggs are laid.

This heron is migratory outside the tropical parts of its extensive range, where it is a permanent resident. The North American population winters in Mexico, the southern United States, Central America, and the West Indies, and the Old World birds winter in tropical Africa and southern Asia.

These birds stand still at the water's edge and wait to ambush prey, mainly at night. They primarily eat small fish, crustaceans, frogs, aquatic insects, and small mammals. During the day they rest in trees or bushes. The New World race is more gregarious outside the breeding season than the nominate race.

They are often found nesting or roosting within cities in avenue trees on busy roads.

The scientific name, Nycticorax, means "night raven", and refers to this species' nocturnal habits and harsh crow-like call.

In the Falkland Islands, they are known as "quarks" which is an onomatopoeic term.