The yellow-breasted flatbill or yellow-breasted flycatcher (Tolmomyias flaviventris) is a passerine bird in the tyrant flycatcher family. It is found in South America, ranging from Colombia and Venezuela south to Peru, Bolivia, and Brazil, and on both Trinidad and Tobago. There are significant variations in its voice and plumage, with western birds duller and more olive, and eastern and northern birds brighter and more ochre-yellow. The two are sometimes considered separate species, the western olive-faced flatbill (or flycatcher), T. viridiceps, and the eastern and northern ochre-lored flatbill (or flycatcher), T. flaviventris.