The Osprey (Pandion haliaetus), also known colloquially as fishhawk, seahawk or fish eagle, is a medium-large fish-eating bird of prey. However, It is not the same as a sea-eagle. It is found on all continents except Antarctica although in South America it occurs only as a non-breeding migrant. It is widely distributed because it tolerates a wide variety of habitats, nesting in any location which is near a body of water and provides an adequate food supply. It is divided into four similar subspecies.

Because the Osprey has many unique characteristics, it has been given its own taxonomic genus, Pandion, and family, Pandionidae. It is a medium-sized raptor, reaching 60 cm (24 in) in length with a 1.8 m (6 ft) wingspan. It is brown on the upperparts and predominantly whitish on the head and underparts, with a brownish eyepatch and wings.

As its other common names suggest, the Osprey's diet consists almost exclusively of fish. It has evolved particular physical characteristics and exhibits some unique behaviours to assist in hunting and catching prey.

The Osprey is 1400-2000 grams (3-4.4 lb) and 52-60 centimetres (20.5-24 in) long with a 150-180 cm (5-5.9 ft) wingspan. The upperparts are a deep, glossy brown, while the breast is white and sometimes streaked with brown, and the underparts are pure white. The head is white with a dark mask across the eyes,reaching to the sides of the neck. The irises of the eyes are golden to brown. The bill is black, with a blue cere, and the feet are white with black talons. A short tail and long, narrow wings with four long, fingerlike feathers, and a shorter fifth, give it a very distinctive appearance.

The sexes appear fairly similar, but the adult male can be distinguished from the female by its slimmer body and narrower wings. The breast band of the male is also weaker than that of the female, or is non-existent, and the underwing coverts of the male are more uniformly pale. It is straightforward to determine the sex of breeding pair, but harder with individual birds.

Juvenile Osprey may be identified by buff fringes to the plumage of the upperparts, a buff tone to the underparts, and a streaked feathers on the head. During spring, barring on the underwings and flight feathers is a better indicator of a young bird, due to wear on the upperparts.

In flight, the Osprey has arched wings and drooping "hands", giving it a gull-like appearance. The call is a series of sharp whistles, described as cheep, cheep or yewk, yewk. Near the nest, the call is a frenzied cheereek!

Fish comprise 99 percent of the Osprey's diet. It typically takes fish weighing 150–300 g (5.3-10 oz) and about 25–35 cm (10-12 in) in length, but the weight can range from 50 to 2000 g (1.7-68 oz). Prey is first sighted when the Osprey is 10-40 m above the water, after which the bird hovers momentarily then plunges feet first into the water. It is able to dive to a depth of 1 meter (3.3 ft). The angle of entry into the water varies with the nature of the prey; steeper, slower dives are used when pursuing deeper, slow-moving fish, while long, quick dives are used for faster surface fish. After catching the fish considerable effort is needed to get airborne again. As it rises back into flight the fish is turned head-forward to reduce drag.

The Osprey has a worldwide distribution. It is found in temperate and tropical regions of all continents except Antarctica. In North America it breeds from Alaska and Newfoundland south to the Gulf Coast and Florida, wintering further south from the southern United States through to Argentina. The Osprey is found throughout Europe north into Scandinavia and Scotland, though not Iceland, in summer and wintering in North Africa. In Australia it is sedentary and found around the coastline, though only a non-breeding visitor to eastern Victoria and Tasmania. In the islands of the Pacfic it is found in the Bismarck Islands, Solomon Islands and New Caledonia, and fossil remains of adults and juveniles have been found in Tonga, where it probably was wiped out by arriving humans. It is possible it may once have ranged across Vanuatu and Fiji as well. It is an uncommon to fairly common winter visitor to all parts of South Asia, Southeast Asia including Myanmar through to Indochina and southern China, Indonesia, Malaysia and the Philippines.

The Osprey is highly successful due to its tolerance of a wide range of habitats. It may nest in any location which is near a body of water and which provides safety and an abundance of fish. Nests are generally found within 3 to 5 km of a body of water, which may be a salt marsh, mangrove swamp, cypress swamp, lake, bog, reservoir or river. Even during migration, Ospreys stay close to water, often following river valleys.

The Osprey is particularly well adapted to this diet, with reversible outer toes, sharp spicules on the underside of the toes, closable nostrils to keep out water during dives, and backwards facing scales on the talons which act as barbs to help hold its catch. The 'barbed' talons are such effective tools for grasping fish that, on occasion, an Osprey may be unable to release a fish that is heavier than expected. This can cause the Osprey to be pulled into the water, where it may either swim to safety or succumb to hypothermia and drown (fish heavier than the Osprey itself are hazardous in this way). Rarely, the Osprey may prey on other wetland animals, such as aquatic rodents, salamanders, other birds, and reptiles as large as young alligators.