The white-throated tyrannulet (Mecocerculus leucophrys) is a species of bird in subfamily Elaeniinae of family Tyrannidae, the tyrant flycatchers.

Their wings are brownish black with cinnamon-buff to yellowish buff edges and tips on the flight feathers.

[7][8][9][10][11][12][13][excessive citations] The white-throated tyrannulet is mostly a resident species but makes some elevational movements during the austral winter or local wet season.

[7][12] The white-throated tyrannulet feeds mostly on insects and spiders but also includes some small fruits in its diet.

It perches upright (unusual for a tyrannulet), and takes most of its food by gleaning from leaves and twigs, sometimes hanging underneath, and sometimes with short flights to briefly hover.

[7][10][11][12][13][excessive citations] The white-throated tyrannulet's breeding season has not been fully defined but spans from December to March in Argentina and possibly as long as January to August in Colombia.

Its nest is a cup made of plant fibers and wool, moss, and spider web.