The white-flanked antwren is a species of bird in subfamily Thamnophilinae of family Thamnophilidae, the "typical antbirds". It is found from Honduras to Panama in Central America, in every mainland South American country except Argentina, Chile, Paraguay, and Uruguay, and on Trinidad.

The antbirds are a large passerine bird family, Thamnophilidae, found across subtropical and tropical Central and South America, from Mexico to Argentina. There are more than 230 species, known variously as antshrikes, antwrens, antvireos, fire-eyes, bare-eyes and bushbirds. They are related to the antthrushes and antpittas, the tapaculos, the gnateaters and the ovenbirds. Despite some species' common names, this family is not closely related to the wrens, vireos or shrikes.