The southern beardless tyrannulet (Camptostoma obsoletum) is a small passerine bird in subfamily Elaeniinae of family Tyrannidae, the tyrant flycatchers.

It is found in Costa Rica, Panama, in every mainland South American country except Chile, and on Trinidad.

Their throat is grayish white and the rest of their underparts mostly pale yellow with a faint olive wash on the breast.

Both sexes of all subspecies have a brown iris, a horn-colored maxilla, a dull orangish or pinkish mandible, and gray legs and feet.

[6][13] The southern beardless tyrannulet feeds mostly on insects and spiders; berries such as those of mistletoe (Loranthaceae) and other small fruits are also a significant part of its diet.

It forages actively, moving frequently as it gleans prey and fruits from a perch; it occasionally takes food while briefly hovering.

They include a "[t]hin, high whistle, 'fleeeeer', rising and falling slightly, sometimes with terminal syllables, 'fleeeeee-pit-pit' " and a "descending series of clear, minor-key notes, 'fleee, flee-fleew-fleew' ".

It has an extremely large range and its estimated population of at least 50 million mature individuals is believed to be stable.

[6] It is considered rare at the northern end of its Costa Rican range, less numerous is eastern Ecuador than western, and uncommon in northeastern Peru.