The scarlet macaw (Ara macao) also called the red-and-yellow macaw, red-and-blue macaw or red-breasted macaw, is a large yellow, red and blue Neotropical parrot native to humid evergreen forests of the Americas. Its range extends from southeastern Mexico to Peru, Ecuador, Colombia, Bolivia, Venezuela, Honduras, and Brazil in lowlands of 500 m (1,600 ft) (at least formerly) up to 1,000 m (3,300 ft), the Caribbean island of Trinidad, as well as the Pacific island of Coiba. Formerly, the northern extent of its range included southern Tamaulipas. In some areas, it has suffered local extinction because of habitat destruction, or capture for the parrot trade, but in other areas, it remains fairly common. It is the national bird of Honduras. Like its relative the blue-and-yellow macaw, the scarlet macaw is a popular bird in aviculture as a result of its striking plumage. It is the third most common macaw species in captivity after the blue-and-yellow and red-and-green macaw respectively. In recent years it has become much rarer in captivity and much more expensive due to stricter laws, its price being higher than even red-and-green macaws.

The scarlet macaw was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Psittacus macao. The scarlet macaw is now placed in the genus Ara (Lacépède, 1799), one of 6 genera of Central and South American macaws.

The two subspecies can be recognized by size and color detail in the feathers on the wings:

In May 2013, it was announced that a team of scientists, led by Dr. Christopher M. Seabury and Dr. Ian Tizard of Texas A&M University had sequenced the complete genome of the scarlet macaw. Based on this genome, species-specific microsatellite genetic markers were developed to aid genetic studies throughout the range of the species. These genetic markers were later validated on the trace amount of DNA acquired from feathers, and applied to study red-and-green macaws in a tropical landscape where DNA can degrade very quickly. These markers were proven to be useful to study their population genetics and identification of individuals in the landscape of the Peruvian Amazon.

It is about 84 centimeters (33 in) long, of which more than half is the pointed, graduated tail typical of all macaws, though the scarlet macaw has a larger percentage of tail than the other large macaws. The average weight is about 1 kilogram (2 lb 3 oz). The plumage is mostly scarlet, but the rump and tail-covert feathers are light blue, the greater upper wing coverts are yellow, the upper sides of the flight feathers of the wings are dark blue as are the ends of the tail feathers, and the undersides of the wing and tail flight feathers are dark red with metallic gold iridescence. Some individuals may have green in the wings. The Central American subspecies is larger and averages 89 cm or (35 in) in length.^{[citation needed]}

There is bare white skin around the eye and from there to the bill. Tiny white feathers are contained on the face patch. The upper mandible is mostly pale horn in color and the lower is black. Juveniles have dark eyes; adults have light yellow eyes.

It is frequently confused with the slightly larger green-winged macaw, which has more distinct red lines in the face and no yellow in the wing.

Scarlet macaws make very loud, high and sometimes low-pitched, throaty squawks, squeaks and screams designed to carry many kilometers to call for their groups.