Kingfishers (Alcedinidae) are a group of 93 species of small to medium sized brightly coloured birds. They have a cosmopolitan distribution, with most species being found in the Old World and Australia. They belong to three different subfamilies:
-River kingfishers (Alcedininae)
-Tree kingfishers (Halcyoninae)
-Water kingfishers (Cerylinae)

Kingfishers occupy a wide range of habitats. While they are often associated with rivers and lakes, over half the worlds species are found in forests and forested streams. They also occupy a wide range of other habitats. The Red-backed Kingfisher of Australia lives in the driest deserts, although kingfishers are absent from other dry deserts like the Sahara. Other species live high in mountains, or in open woodland, and a number of species live on tropical coral atolls.

The plumage of most kingfishers is bright, with green and blue being the most common colours. The brightness of the colours is neither the product of iridescence (except in the American kingfishers) or pigments, but is instead caused by the structure of the feathers, which causes scattering of blue light (the Tyndall effect).

The kingfishers have a long, dagger-like bill. The bill is usually longer and more compressed in species that hunt fish, and shorter and more broad in species that hunt prey off the ground. The largest and most atypical bill is that of the Shovel-billed Kookaburra, which is used to dig through the forest floor in search of prey. The kingfishers have excellent vision; they are capable of binocular vision and are thought in particular to have good colour vision. They have restricted movement of their eyes within the eye sockets, instead using head movements in order to track prey. In addition they are able to compensate for the refraction of water and reflection when hunting prey underwater, and are able to judge depth underwater accurately. They also have nictitating membranes that cover the eyes when they hit the water in order to protect them; in the Pied Kingfisher has a bony plate which slides across the eye when the bird hits the water.

A number of species are considered threatened by human activities and are in danger of extinction. The majority of these are forest species with limited distribution, particularly insular species. They are threatened by habitat loss caused by forest clearance or degradation and in some cases by introduced species. The Marquesan Kingfisher of French Polynesia is listed as critically endangered due to a combination of habitat loss and degradation caused by introduced cattle, and possibly due to predation by introduced species.