The red-winged blackbird is a passerine bird of the family Icteridae found in most of North America and much of Central America. It breeds from Alaska and Newfoundland south to Florida, the Gulf of Mexico, Mexico, and Guatemala, with isolated populations in western El Salvador, northwestern Honduras, and northwestern Costa Rica. It may winter as far north as Pennsylvania and British Columbia, but northern populations are generally migratory, moving south to Mexico and the Southern United States. Claims have been made that it is the most abundant living land bird in North America, as bird-counting censuses of wintering red-winged blackbirds sometimes show that loose flocks can number in excess of a million birds per flock and the full number of breeding pairs across North and Central America may exceed 250 million in peak years. It also ranks among the best-studied wild bird species in the world. The red-winged blackbird is sexually dimorphic; the male is all black with a red shoulder and yellow wing bar, while the female is a nondescript dark brown. Seeds and insects make up the bulk of the red-winged blackbird's diet.

Icterids or New World blackbirds make up a family, the Icteridae, of small to medium-sized, often colorful, New World passerine birds. The family contains 108 species and is divided into 30 genera. Most species have black as a predominant plumage color, often enlivened by yellow, orange, or red. The species in the family vary widely in size, shape, behavior, and coloration. The name, meaning "jaundiced ones" comes from the Ancient Greek ikteros via the Latin ictericus. This group includes the New World blackbirds, New World orioles, the bobolink, meadowlarks, grackles, cowbirds, oropendolas, and caciques.