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 Palestine, Libya and Gambia.

Red kites are 60 to 70 cm (24 to 28 in) long with a 175–195 cm (69–77 in) wingspan; males weigh 800–1,200 g (28–42 oz), and females 1,000–1,300 g (35–46 oz). It is an elegant bird, soaring on long wings held at a dihedral, and long forked tail, twisting as it changes direction. The body, upper tail and wing coverts are rufous. The white primary flight feathers contrast with the black wing tips and dark secondaries. Apart from the weight difference, the sexes are similar, but juveniles have a buff breast and belly. Its call is a thin piping sound, similar to but less mewling than the common buzzard. There is a rare white leucistic form accounting for approximately 1% of hatchlings in the Welsh population, but this variation confers a disadvantage in the survival stakes.

Adults differ from juveniles in a number of characteristics:

Adults are overall more deeply rufous, compared with the more washed out colour of juveniles;

Adults have black breast-streaks whereas on juveniles these are pale;

Juveniles have a less deeply forked tail, with a dark subterminal band;

Juveniles have pale tips to all of the greater-coverts (secondary and primary) on both the upper- and under-wings, forming a long narrow pale line; adults have pale fringes to upperwing secondary-coverts only.

These differences hold throughout most of the first year of a bird's life.