The red kite (Milvus milvus) is a bird of prey in the family Accipitridae, which also includes many other diurnal raptors such as eagles, buzzards, and harriers. The species currently breeds only in Europe, though it formerly also bred in west Asia and northwest Africa. Historically, it was only resident in the milder parts of its range in western Europe and northwestern Africa, whereas all or most red kites in northern mainland Europe wintered to the south and west, some also reaching western Asia, but an increasing number of northern birds now remain in that region year-round. Vagrants have reached north to Finland and south to Israel, Libya and the Gambia.

The English word "kite" is from the Old English cyta which is of unknown origin. A kite is mentioned by Geoffrey Chaucer in his Knight's Tale. The early 15th century Hengwrt manuscript contains the lines: "Ther cam a kyte, whil þt they were so wrothe That bar awey the boon bitwix hem bothe." The first recorded use of the word kite for the human-operated aerial device dates from the 17th century.

The red kite was described by the Swedish naturalist Carl Linnaeus in 1758 in the 10th edition of his Systema Naturae under the binomial name Falco milvus. The word milvus was the Latin name for the bird. In 1799 the French naturalist Bernard Germain de Lacépède moved the species to the genus Milvus creating the tautonym.

Two subspecies are recognised:

The subspecies M. m. fasciicauda is almost certainly extinct.

The genus Milvus contains two other species: the black kite (M. migrans) and the yellow-billed kite (M. aegyptius). The red kite has been known to successfully hybridize with the black kite in captivity where both species were kept together, and in the wild on the Cape Verde Islands and infrequently in other places.

The red kites on the Cape Verde Islands are (or rather were) quite distinct in morphology, being somewhat intermediate with black kites. The question whether the Cape Verde kite should be considered a distinct species (Milvus fasciicauda) or a red kite subspecies has not been settled. A mitochondrial DNA study on museum specimens suggested that Cape Verde birds did not form a monophyletic lineage among or next to red kites. This interpretation is problematic: mtDNA analysis is susceptible to hybridization events, the evolutionary history of the Cape Verde population is not known, and the genetic relationship of red kites is confusing, with geographical proximity being no indicator of genetic relatedness and the overall genetic similarity high, perhaps indicating a relict species. Given the morphological distinctness of the Cape Verde birds and that the Cape Verde population was isolated from other populations of red kites, it cannot be conclusively resolved as to whether the Cape Verde population was not a distinct subspecies (as M. migrans fasciicauda) or even a species that frequently absorbed stragglers from the migrating European populations into its gene pool. The Cape Verde population became effectively extinct since 2000, all surviving birds being hybrids with black kites.

The genus Milvus contains two other species: the black kite (M. migrans) and the yellow-billed kite (M. aegyptius). The red kite has been known to successfully hybridize with the black kite in captivity where both species were kept together, and in the wild on the Cape Verde Islands and in other places.