The yellow-winged blackbird (Agelasticus thilius) is a species of bird in the family Icteridae. It is found in Argentina, Bolivia, Brazil, Chile, Paraguay, Peru, and Uruguay.

The species' natural habitats include marshes and pastureland. Adult males are black-plumaged except for bright yellow epaulets and the corresponding feather tracts on the underside of the wing. Adult females are brown and streaky, while immature males are similar to females in plumage, but with the addition of the adult male's yellow wing patches.