The genus Empidonax is a group of small insect-eating passerine birds in the tyrant flycatcher family, the Tyrannidae. The genus name Empidonax is from Ancient Greek empis, "gnat", and anax, "master".[2]
Most of these birds are very similar in plumage: olive on the upper parts with light underparts, eye rings and wing bars. In the nesting season they may be distinguished by range, habitat and call; in other situations, particularly on migration and in winter, it may not be possible to be sure of specific identification.
Euler's flycatcher, Lathrotriccus euleri and gray-breasted flycatcher, Lathrotriccus griseipectus were formerly placed in Empidonax, but differ anatomically and biochemically and are now placed in the genus Lathrotriccus.